DE1917119C - Diode gate circuit for large signal bandwidth - Google Patents

Description

th diodes, facilities for generating

generation of a bias voltage blocking the diodes

and one at the junction of the two.

Series branch diodes connected cross branch «» The invention relates to a controllable diode lor-

with a third diode, 'via which a control signal circuit for large signal bandwidth, with one of

can be supplied, which, overcoming the blocking signal input, outgoing series branch, the

The diodes of the series are connected in series with two oppositely

branch put into the conductive state, has dipped diodes, devices for generating

characterized in that the other »5 a bias voltage blocking the diodes and a

Diode (D 3; with opposite electrode as at the connection point of the two series diodes

the series branch diodes (D 1, D 2) connected to the connecting branch with a third diode,

connection point is connected, in the blocking direction via which a control signal can be supplied, which is below

is biased and by a Tastimpulsgene- overcoming the blocking bias

rator (G) is fed with pulse control signals, ao diodes of the series branch in the conductive state

that at the connection point a termination is added.

impedance (R 2, C2) is connected, whose foot- In such a gate circuit is the distance

point by a leakage leading to ground between the input and the output normal-

Capacitor (C 2) blocked with a relatively large capacity. This route done in a familiar way

zität is formed that at the output (3) that in as is opposed by a series connection of two

Series connection of polarized diodes, which are connected by a bias

two diodes (Dl, D 2) a voltage lying to ground are kept in the blocking state, is by a

Storage capacity (C j) is connected, and normally pulse-shaped control signal conductive

that the output (3) is made to a signal recovery, so that a useful

circuit is connected, the off signal of which is switched through to the output,

output signal at least in part on the diodes Da between the output and earth, in particular

(Dl, D2, D3) is fed back. at higher frequencies, a noticeable stray capacitance

2. Diode gate circuit according to claim 1, there is da- zität and there is also when the gate is open characterized in that the discharge capacitor circuit has an impedance between the input and Sator has a capacitance (C 2) of more than 300 pF 35 output, the gate circuit has a time and that the negative feedback has a band constant which is determined by the product of the stray capacitance width of more than 0.5 GHz. and the insulation resistance of the blocked

3. Diode gate circuit is determined according to claim 1 route. By the impedance of the signal or 2, characterized in that the bias voltage connected to the source which connects the useful signal to the input of the gate further diode (D 3), this time constant can be changed is. increases. During the time interval in which the

4. Diode gate circuit occurs after one of the touch pulse, the stray capacitance is charged by Proverbs 1 to 3, characterized in that the input signal is charged. However, since the time-signal recovery circuit has a difference in duration of the sampling pulse at high signal frequencies amplifier (TR 1, TR 2) that is between 45 and 45, the charge and thus the output signal generated at output (3) and another amplifier is the output signal smaller than the input signal. Fer- (A) the signal recovery circuit occurs when using diodes for a dertet, with one input of the differential amplifier-like gate circuit distorting the output to output (3) and the other input to signals due to the non-linear characteristic of the diode the negative feedback is connected. 50 on.

5. Diode gate circuit according to claim 4, that the shorter the period of the key pulse, the more characterized that the differential amplifier can be the higher the frequency of the signal that the ker two field effect transistors (TR 1, TR 2) output is removed. Therefore, one of the has. like gate switching over a large bandwidth

6. Diode gate circuit can be operated according to one of the An 55, but the output signal is Proverbs 1 to 5, characterized in that the smaller and smaller because of the time constants. For the series connection of two oppositely polarized connections between the bandwidth / ₀ or the most highly polarized diodes (Dl, D 2), a further series of transmittable frequencies and the pulse interconnection of oppositely polarized, by val τ, the following applies:

a bias blocked diodes (D 3, D 4) 60 _r . ; = ο 44

connected in parallel to form a diode bridge

tet and that a sixth diode (D 6) is present. If τ is equal to 60 psec, then / _{0 is} equal to 7 GHz.

can be seen, which are equipped with an opposite electrode such as a gate circuit for such a bandwidth

the series branch diodes of the other series switching diodes. During the lock state, a

connected to the connection point, in 65 diode a capacitance of about 0.5 pF and one

Reverse biased and also by the resistance of a few megohms, so that the input

Key pulse generator (G) with pulse control signals output signal as a leak signal via the impedances to the

cesDeist is. Exit. Due to the time constants of the

I 917 119

Gate circuit is now this leakage signal off, a control voltage is applied to the electronic

output signal superimposed A happened at the output switch, depending on the sign of the

teter low frequency amplifier thus amplifies the control voltage of the T-shaped attenuator

Sum of both signals, so that a distortion has high or low attenuation, so that

As mentioned above, the waveform yields significant power to the load

out, the output signal is the smaller, depending or not. In this circuit arrangement, the im

higher the frequency, so that the output signal is not suitable for the diode lying across the branch

is strongly influenced by the leak signal, namely control voltage source to intercept reflected waves

the stronger the higher the frequency ir ?. This result because the diode has the same forward direction as

The appearance also applies if the io has the other diodes at the output (German patent

Gate circuit a storage capacity is connected, 830352).

In another known circuit arrangement

to make gangs-stray capacitance independent. are two in series, oppositely polarized

The control signal for such a diode gate diodes is provided, at their common connection

circuit, mostly in the form of a test pulse, 15 connection point tactile pulses are applied, the one at

the connection point of the two series branches - touch the series connection occasionally DC voltage.

diodes fed. The impedance of the key pulse at the output of the Diodensi.haltung is a triode

generating key pulse generator, seen from the switched, whose grid is controlled by the key pulses

a connection point off (output impedance of the push button is controlled and its anode voltage corresponds

Ϊ pulse generator «), is small and strong, depending on the frequency with which the probe pulses have a pulse course.

frequency dependent. Even if the first series branch- The amplitudes of the pulses represent a measure

if diode is blocked, this output impedance a's acts for the level of the direct voltage

Load for the signal input via the capacitance of the circuit arrangement is essentially used for

f diodes, creating the waveform of the Tasicn to be measured by direct voltages and is used for keying

Input signal is distorted, so that irregular as is not suitable for particularly high-frequency signals

Factors arise in the frequency characteristic in (USA.-Patent 2 950690).

High frequency range. On the other hand it is scl.wie- There is also a known diode switch with two

rig. the output impedance of the pulse generator connected in series, with opposite polarity

j adapt over a wider range. With other diodes, at their connection point in the cross branch

! In other words, the ripple factor is great. Around 30 a third diode is connected. A control voltage

j To make the pulse width of the key pulse smaller, is on the common connection point of the

a diode is normally provided in the pulse generator and thus blocks or opens the

Shortening circuit used to switch the pulse diode. Especially with very high fre-

width to be reduced to a time interval, which occurs from sequences a reflection of a wave of the entrance

the signal is required to send the shortening switching signal to the control voltage generator, which is carried out by

movement forward and backward. The well-known diode switch is not attenuated or

Ripple factor of this abbreviation: circuit is each can be suppressed (asutsche Auslegeschrift

but infinite, so that total reflection occurs. Da 1 084 309).

this reflection on the capacitance of the diode in the there is a diode switch in a bridge circuit be-blocking state causes a load on the input, 40 knows, in which to divert a leakage current becomes part of the input signal that is sent to the input via a transistor with a low impedance pending, from the pulse generator with the connection points of the opposite polarity Shortening circuit reflected back to the input. Diodes is placed and to which also a Steuerspanso that the reflected wave is connected to the input signal voltage. In this known scarf is superimposed and a distortion of the shaft arrangement is prevented that a form results when the gate circuit opens. On this large part of the leakage current to the output of the In this way, the high-frequency characteristic of the gate switch is used for a scanning process, in particular irregular and further deteriorated. cere at very high frequencies, it is not An attempt to solve this problem could be suitable (German Auslegeschrift 1 182120). consist of a broadband damping device with so. Finally, a diode switch is in a small ripple factor between the key bridge retention also known to switch the control panel pulse generator and the gate circuit. voltage to the bridge circuit via a diode When put an attenuator with an attenuation of. However, this diode has the same pole If 6 db were used, the reflected wave could be like the others at the common connection point can be reduced to a quarter. But if the probe is located, there can be reflections from the control voltage pulse that is fed to the gate circuit, if the source back to the signal input would not also be attenuated by half. Therefore to prevent them.

It is therefore the object of the invention to hold a diode that it would have without an attenuator, gate circuit for the most accurate possible sampling of the pulse generator must have pulses with the two-Go signals of large bandwidth (or high upper generate times the amplitude. However, this is practically- limit frequency) to create, table very difficult to carry out. In a diode gate circuit of the type mentioned at the outset, this object is achieved in that Load switched electronic switch known, which has the further diode with opposite electrode is designed as a T-shaped attenuator in 65 like the series branch diodes at the connection point a diode is connected to each branch. The diode connected is reverse biased are with the same electrodes on the common and voa a Tastimpuisgenerator with pulse connection point. Control signals are fed via the diode in the shunt arm that

connection point a terminating impedance is connected, the base of which is formed by a discharge capacitor leading to ground of relatively large capacitance that at the output of the series connection of the two provided in the series branch Diodes is connected to a grounded storage capacitance and that the output is connected to a signal recovery circuit whose Output signal is at least partially fed back to the diodes.

With the diode gate circuit according to the invention, a negative feedback broadband gate circuit is created, which is used for sampling and recovery of high and ultra-high frequency signals and can be used, for example, for sampling oscilloscopes. However, there are also numerous other possible applications, for example as an analog-to-digital converter, using the pulse signals obtained during sampling directly be, d. H. before their reassembly. In this case, the reassembly becomes one Continuous (analog) signal is only important for negative feedback, i.e. H. for correcting the non-linear distortion caused by the diodes.

In the gate circuit according to the invention, the difficulties that would otherwise be avoided with very high frequencies, due to the influence of intrinsic and stray capacitances. Transit times and signal reflections appear. This benefit is achieved through three main features. For one, there is the leakage current due to the stray capacitance of the diodes via a low-resistance shunt branch, so that a relatively favorable attenuation ratio of a sampled signal is achieved. Second, the im Transverse branch with an opposite electrode as the series branch diodes connected diode causes a signal return from the sampling pulse generator to the signal input, which would result in a distortion of the waveform of the useful signal. The third will eventually a signal recovered from the output pulses of the gate circuit is fed back. Through this in particular, the disadvantage caused by the non-linearity of the diodes is eliminated.

Embodiments of the invention will now be discussed described with reference to the drawings It shows

Fig. 1 is an electrical circuit diagram of an embodiment of the invention.

FIG. 2 shows an equivalent sound image of the circuit shown in FIG.

F i g. 3 shows an equivalent circuit diagram of the circuit diagram shown in FIG. 1 without the resistor R 1 and the diode D 3.

F i g. 4 shows a graph of the characteristic and the waveforms on diode D 3 and

5 shows the circuit of a modified embodiment of the invention.

In the in F i g. 1 shows an input 1 for a signal that is to be measured, a ground connection 2 and an output 3 at which the amplitude of the signal to be measured is picked up during the duration of the probe pulse. The output 3 is connected to the control electrode of a field effect transistor TRl. The circuit also has three diodes DI, Dl and D3, of which the diodes 1 and 2 are connected in series and have opposite polarity, while the third Diode 3 with the opposite electrode as the series branch diodes Dl and D2 is connected to their connection point. The diodes 1, 2 and 3 are connected via nodes 7, 8 and 9 to one Bias voltage that normally blocks the diodes holds.

The bias on the diodes is applied via resistors R 2, R 3, RS and R 1 and via bias sources £ 1, £ 2 and £ 3. A key pulse

generator G feeds the diode D 3 via a terminal 4 with a negative key pulse which exceeds the bias voltage generated by the bias sources El, £ 2 and £ 3 and thus makes the diodes conductive. A storage capacitor C 3 between the

is output 3 and ground stores the signal to be measured that has passed through. A capacitor C1 at the output of the pulse generator prevents. a bias voltage is applied to the pulse generator G. Furthermore, at the connection point of the two

ao connected to the series branch diodes Dl and Dl via a resistor Rl a discharge capacitor C2, the base of which is connected to ground.

The capacitance between the terminals of the diodes Dl, Dl and D3, while they are blocked,

5 are indicated by C 4, C 5 and C 6, while the insulation resistances of the diodes D 1 and D 2 are indicated by R 4 and R 6, respectively

The field effect transistors TR 1 and TR1 form a differential amplifier. The control electrode of the The transistor TR 2 is connected to a circuit point 8 via a resistor R 7. The source electrodes are connected to one another and connected to a current source P p via a resistor R 9. The drainage electrodes of the transistors TR 1 and TA 2 are connected to a current source + B via resistors R 8 and R iO, respectively. The drain electrode of the transistor TR1 is connected to an AC amplifier A , the output of which is fed to a signal shaper. The S tnal

4u former S is used to store and hold the peak value of the output signal coming from the AC amplifier, ie a smoothing of the output pulse sequence for the purpose of signal recovery.

at the connection 5 and on the other hand (. s negative feedback via a resistor / 711 and the bias source £ 3, which is fed back with a Pole is at the connection point 6 between the resistor Λ11 and a resistor Λ12.

so that form an attenuator. The other pole of the bias voltage source is at connection 7 between the two other bias voltage sources E 1 and E 2

The capacitances C4, CS and C 6 of the diodes Dl. D 2 and D 3 have a value of about 0.5 pF.

The resistor R 2 is matched to the output impedance of the pulse generator G and has a value of about 50 ohms. The input 1 is due to an impedance adapted to the signal source in the size

Order of 50 ohms completed. The capacitance of the bypass capacitor can have a value of several tens of pF, but it is advantageous to choose this value much higher, for example about 1000 pF. The capacitance C4 and the resistance R 4

lie in the series branch as a series element of an L-attenuator, while the resistor K 2 and the capacitor C 2 deo form shunt branch, so that due to the existing impedance values this

(ο

Attenuator the attenuation ratio is avoided extremely Wcllenformen. The attenuation of the

is large, so that the leakage pulse flowing to the output when the diodes are conducting is very small,

current through the blocked diodes Dl and Dl strong The Stromspannungskcnnlinien of the diode D3 as

The other diodes D1 and D2 are also fed to the alternating amplifier and are not linear

will. If the leakage current is below 5 in frequency (Fig. 4). Therefore, if the key pulse to this diode

the lower or above the upper frequency limit c D 3 is applied, one obtains a much steeper one

of the AC amplifier, then it becomes pulse as the applied waveform. The amplitude

not amplified by the inverter, such as the pulse transmitted by diode D 3

that he alone processes the useful signal. This can also be accessed by changing the created template

Way, the low-frequency operated amplifier receives voltage to be changed.

kcr hardly any or only a very small interfering signal. As in Fig. Is 1, the bias Fig. 2 shows an equivalent circuit diagram of the show in FIG. 1 GC via the resistor R3 to the connection point circuit, and F i g. 3 shows a salt switch between the resistor R 2 and the Ableitkonbild for the circuit shown in Fig. 1, the densalor ('2 applied. This bias can depending on the resistor R 1. the diode D3 and the bias 15 but also directly at the connection point between source /: 1 are omitted and the capacitor C1 is connected to the diodes D 1 and D 2 via a corresponding coupling to the connection point between the diodes D 1. It is also possible and /) 2 is connected. In the river. 2 and 3, Zl represents the polarity of the diodes Dl, D2 and D3 and the impedance of an input stage. Signalqucllc Z2 key pulse and to apply the corresponding impedance through the resistor Λ 2 uno the ao the bias voltages. Capacity Cl formed stage. Z 3 the output The negative feedback signal Vf, which is from the Verimpcdanz des Tastimpulsgcncrators. Z 4 is an impedance point 6 between the resistances All dan / the capacitance C 4 (since the resistance R4 and R 12 (Fig. 1) is fed back, it has a sign that is just greater than the impedance of the capacitance C "4 Input signal 1-7. The signal Vf ν ·. Is this impedance at high frequencies veras has a waveform which is an increase in the negligible) and ZS corresponds to the impedance of the capacitance interval of the input signal Vi , and C "5. The impedance Zl is essentially constant over the entire frequency band, if the point in time of a blanking is considered, while Vf Vi applies. An impedance Z4 and ZS of the signals V] and Vi will be reduced by the diodes D1 and D2 as the frequency rises. On the other hand, the conductors 30 also changes, the impedance Z 3 caused by the AC amplifier changes strongly with the frequency. This is generated strengthens and stored by the signal shaper an irregularity in the frequency response on and is kept. In this way, a wave input becomes 1. so that the reflected wave of the input shape is superimposed on an enlargement of the interval of the level. output signal Vi , or a waveform which in FIG. 3 is equal to signal Vi at below 0.5 GHz is generated at the output 5. Frequencies the impedance Z4 sufficiently large so that the signal Vf is thus a negative feedback signal, the useful signal that is to be measured and if the signal Vf is via the amplifier and input 1, with the diodes blocked, it is hardly fed back to the signal shaper without its spigot point 2 appears. The relatively small value would have been stored if the signal Vf had the same signal is reflected at the impedance Z3 and has a sign like the signal Vi, so that a back signal is attenuated when it passes through the impedance Z4. coupling would be obtained. The consequence of this would be that, for this reason, there would be essentially no vibrations. In order to prevent this from happening, the reflected wave has an effect on each other. is, as in Fig. 1 shows a differential amplification 1. However, if the frequency is provided above about 1 GHz, which is increased by the field effect transistors, the ^f mpcdanzZ4 becomes smaller, so that 45 TR 1 and TR1 are formed. Another possibility of a significant part of the pending signal from the ability is to pass the AC amplifier with impedance Z4 and derived from the impedance of a difference between a signal component reflected by the impedance Z 4 from the input signal Vi 23 at point PI, and a will. The signal is attenuated when it runs in the forward direction frequency component of the signal Vf with a strong reduction from point Pl to point P 2, and it is applied at a higher frequency, or it is further attenuated when it goes from point P 2 to differential amplifier together with the change point Pl runs back. These attenuations are to be used with every current amplifier. Only that cannot be great here. They correspond to those of 2 π Difference signal between the signals Vi and Vf ver attenuation stages. However, if the impedance Z 5 is added, SS to achieve the non-linear characteristics of the as shown in Fig. 2, the signal, even with diodes DI and D2, will effectively balance. When the frequency is increased, more and more attenuated. the voltage across diode D3 (Fig. 1) if it were not kept at a constant value from point P1 to point P 2, from point P 2, to point P 3. from point P 3 to point P 2 and from the amplitude of the key pulse at VerPunkt P 2 runs to point Pl. This has the consequence that the connection point between the diodes D1 and D2 would be linearly distorted down to a very small value so that the size of the reflected wave, which changes to the input, so that the output signal does not return. By setting the signal Vf. This effect corresponds to that which two λ attenuation stages connected to the cathode of the diode series via the resistor RI would have. D 3 is applied, the voltage at the diode D 3. Therefore, the frequency characteristic of the gate switch is kept at a constant value, so that the non-linear distortion is eliminated, especially at very high frequencies, so that also the momentum transmission property The in FIG. S further embodiment shown th are greatly improved and a distortion of a circuit has a bridge circuit from the

four diodes Dl, D 2, D 3 and D4. The connection point between the diodes D 1 and D 3 is connected to the input 1. The output 2 of the bridge is connected to the control electrode of the field effect transistor TR1 . The connection points between the diodes Dl and Dl or D3 and D4 are connected to the bias terminals 3 and 4 via the resistors R 2 and R 3 or R 4 and R 5 (similar to FIG. 1). These connection points are also connected to the bias terminals 5 and 6 via the resistor R 1 and the diode D6 (which corresponds to the diode D3 in Fig. 1) and via the resistor R 6 and the diode D 6 (which the diode D3 in Fig. 1) and connected to the connections 7 and 8, via which the key pulse is fed in via the decoupled capacitors C1 and C5. The capacitances C 2 and CA correspond to the capacitance C2 in FIG. 1, and the capacitor C 3 corresponds to the bypass capacitor C3 of FIG.

10

The bias voltage source E 1 Hegt between the terminals 3 and 5, the bias £ 3 between the terminals 4 and 6 (the sources of El and £ 3 correspond to the source El of Fig. 1) and.

the bias voltage El and EA are situated between the terminals 3 and 4. The negative feedback signal is supplied from the connection point between the resistors R 11 and Λ12 to the connection point between the bias sources

ίο El and El · led. Other components of the circuit and their operation are identical to those described in connection with FIG.

In the circuit shown in Fig. 1, the

Input line via the connection point between the diode D 3 and the resistor /? 2 and the connection point between diodes D 1 and D 2 are switched on. The input line can also be connected between the diode D3 and the resistor R1 . Similar connections are

ao also possible with the circuit according to FIG. 5.

1 sheet of drawings

Claims (1)

ι 2 patent claims · ■ 7 'diode gate circuit according to spoke 6, da- vatentansprucne. duj.chseiixmag.i <j! imt that those on the sixth 1. Controllable diode gate circuit for large diode (D6) Hegende bias voltage changes signal bandwidth, with one of a signal bar. input outgoing longitudinal branch, which is a 5
Series connection of two oppositely polarized