CN103248330B - A kind of programmable gain amplifier of high-gain precision - Google Patents

Abstract

The invention discloses a programmable gain amplifier with high gain precision and belongs to the field of semiconductor integrated circuit design. It is mainly used to meet the high gain accuracy requirements of the programmable gain amplifier in the communication system. The structure is formed by cascading a programmable gain amplifier stage with precise adjustable gain and three fixed gain amplifier stages for coarse adjustment. The input signal first determines the approximate gain by switching three fixed gain stages, and then performs precise gain adjustment by the programmable gain stage on this basis, so as to obtain a high-precision gain. Among them, the programmable gain amplifier stage with precise and adjustable gain can obtain precise gain through switch control of the strength of the feedback resistor network, and the three fixed-gain amplifier stages can be roughly adjusted through switch gating. The invention has the advantages of high gain precision, simple gain control, good linearity and the like.

Description

A Programmable Gain Amplifier with High Gain Accuracy

technical field

The invention belongs to the field of semiconductor integrated circuit design, in particular to a programmable gain amplifier with high gain and precision.

Background technique

In fields such as wireless communication, disk reading, and medical equipment, the signals to be processed by analog systems often have a large dynamic range. For example, a gain change of about 80dB is required in a GSM radio receiver. In order to obtain a relatively constant signal, a variable gain amplifier (Variable Gain Amplifier, VGA) is needed to adjust the amplitude of the received signal. Specifically, a control signal is generated by comparing the output signal of the VGA with the reference signal, and the gain of the VGA is controlled so that the amplitude of the output signal is equal to the reference signal. Therefore, the higher the gain accuracy of the VGA, the greater the dynamic range of the gain, the better the dB linearity of the gain with the control signal, and the better the adjustment performance of the received signal.

According to the gain control method, the variable gain amplifier can be divided into a variable gain amplifier (Variable Gain Amplifier, VGA) with continuously adjustable gain, and a programmable gain amplifier (Programmable Gain Amplifier, PGA) with step-change gain. The control signal of the VGA is an analog signal, and the gain is continuously adjustable, but the gain control is complicated; the control signal of the PGA is a digital signal, so its gain varies discretely, but the gain control is simple.

Figure 1 shows a variable gain amplifier based on an attenuator structure. The variable gain amplifier includes a resistor network attenuator, a variable transconductance unit array composed of differential pairs, a transimpedance amplifier and a transconductance controller. The output of each stage of the attenuator is connected to the positive input terminal of a differential pair, and the outputs of all differential pairs are connected together, and the total small signal current generated by it is sent to the transimpedance amplifier to generate a voltage signal, and is fed back to each Negative Input for Differential Pair. The transconductance controller controls each variable transconductance unit separately so that its transconductance varies from zero to the maximum value. Only two variable transconductance modules are turned on at any moment, and the final output voltage is determined by the transconductance ratio of the two variable transconductance modules.

The structure first uses the attenuator to complete a rough adjustment to obtain several large gain steps, and then fine-tunes within this step, so that it only needs to keep the continuous gain adjustable within one attenuator step, so it can be obtained High gain accuracy. But the gain accuracy of this structure depends on the transconductance controller, and only when the transconductance controller satisfies the required functional relationship can dB linear gain control be obtained.

Contents of the invention

Purpose of the invention: The purpose of the present invention is to propose a programmable gain amplifier with high gain precision, so as to meet the high gain precision requirement of the programmable gain amplifier in the communication system.

Technical solution: In order to achieve the purpose of the above invention, the high-gain precision programmable gain amplifier used in the present invention is formed by cascading a programmable gain amplifier stage with precise adjustable gain and three fixed-gain amplifier stages for coarse adjustment; The amplifier circuit has positive and negative two-way input and output, and the two-way circuits are completely symmetrically designed, and the negative input and output signal processing circuits are:

In the programmable gain amplifier stage with precisely adjustable gain, the eleventh switch is respectively connected between the signal negative input terminal and the first resistor, and the other terminal of the first resistor is connected to the inverting input terminal of the first operational amplifier, The positive output terminal of the first operational amplifier is connected to the twelfth switch, and the other end of the twelfth switch is the output terminal of the current stage, and is connected to the reverse input terminal of the second operational amplifier through the eighth first switch, and the positive output of the second operational amplifier is The terminal is connected to the eighth and second switch, and the other end of the eighth and second switch is the output terminal of the current stage, and is connected to the reverse input terminal of the third operational amplifier through the ninth first switch, and the positive output terminal of the third operational amplifier is connected to the ninth and second switch , the other end of the ninth and second switch is the output end of this stage, connected to the inverting input end of the fourth operational amplifier through the first zero and one switch, the positive output terminal of the fourth operational amplifier is connected to the first zero and two switches, and the first zero and one The second switch is the output terminal of the amplifier, connected to the signal negative output terminal;

Among them, 6 groups of feedback switch resistance networks composed of switches and resistors in series are connected in parallel between the input terminal and the output terminal of the first operational amplifier, and the first group is composed of the second first switch, the second resistor, and the second second switch in series ; The second group is composed of the third first switch, the third resistor, and the third and second switches in series; the third group is composed of the fourth first switch, the fourth resistor, and the fourth and second switches in series; the fourth group is composed of the fifth first switch, The fifth resistor and the fifth and second switches are connected in series; the fifth group is composed of the sixth first switch, the sixth resistor and the sixth and second switches in series; the sixth group is composed of the seventh first switch, the seventh resistor and the seventh and second switches in series ; One end of the reverse first switch is connected between the eleventh switch and the signal negative input terminal, and the other end is connected between the twelfth switch and the eighth first switch; one end of the reverse eighth switch is connected between the twelfth switch Between the switch and the eighth first switch, the other end is connected between the eighth second switch and the ninth switch; one end of the reverse ninth switch is connected between the eighth second switch and the ninth first switch, and the other end is connected to the Between the 92nd switch and the 101st switch; one end of the reverse tenth switch is connected between the 92nd switch and the 101st switch, and the other end is connected between the 102nd switch and the signal negative output terminal between.

The eleventh switch to the first and zero second switches all adopt CMOS transmission gate circuits, which are turned on at a low level; the reverse switch adopts a CMOS transmission gate circuit, which is turned on at a high level.

The first operational amplifier adopts a structure of two-stage operational amplifier plus active negative feedback, wherein the first-stage operational amplifier adopts a folded cascode structure, and the second-stage operational amplifier adopts a common-source stage structure of a current source load ; The feedback circuit generates a corresponding feedback signal to the current source load terminal of the second-stage operational amplifier according to the difference between the output common-mode signal and the input reference voltage, thereby adjusting the output common-mode signal to approach the input reference voltage.

In the described fixed-gain amplifier stage for coarse adjustment, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier adopt differential amplifiers with source-level negative feedback resistors, and the differential pair of input transistors passes through the source stages of the resistors. connected, the output is loaded with a PMOS current source, and the gate of the PMOS is connected to the differential output through two resistors.

Beneficial effects: the present invention amplifies the input signal by switching and gating one or several stages of the three fixed gain stages to obtain an approximate gain, and then performs precise gain adjustment by the programmable gain stage on this basis, thereby obtaining A high-precision gain, the structure has the advantages of high gain accuracy, simple gain control, and good linearity.

Description of drawings

Fig. 1 is a kind of variable gain amplifier structure based on attenuator structure;

Fig. 2 is a kind of high gain precision programmable gain amplifier structure provided by the present invention;

Fig. 3 is the gain characteristic curve of programmable gain amplifier of the present invention;

Fig. 4 is a gain error curve of the programmable gain amplifier of the present invention under different gains.

Detailed ways

In order to further illustrate the advantages of the present invention and the specific technical means adopted, the specific implementation and circuit structure of the present invention will be described in detail below in conjunction with the drawings.

Referring to FIG. 2 , a programmable gain amplifier with high gain precision provided by the present invention is formed by cascading a programmable gain amplifier stage with precise adjustable gain and three fixed gain amplifier stages for coarse adjustment. The amplifier circuit has positive and negative two-way input and output, and the two-way circuits are completely symmetrically designed, and the negative input and output signal processing circuits are:

In the programmable gain amplifier stage with adjustable gain, the eleventh switch S11 is respectively connected between the signal negative input terminal Vin and the first resistor R1, and the other end of the first resistor R1 is connected to the reverse input of the first operational amplifier OP1 terminal, the positive output terminal of the first operational amplifier OP1 is connected to the twelfth switch S12, and the other end of the twelfth switch S12 is the output terminal of the current stage, and is connected to the reverse input terminal of the second operational amplifier OP2 through the eighth first switch S81 , the positive output terminal of the second operational amplifier OP2 is connected to the eighth and second switch S82, and the other end of the eighth and second switch S82 is the output terminal of the current stage, and is connected to the inverting input terminal of the third operational amplifier OP3 through the ninth first switch S91, the second The positive output terminal of the three operational amplifiers OP3 is connected to the ninth and second switch S92, and the other end of the ninth and second switch S92 is the output terminal of the current stage, and is connected to the reverse input terminal of the fourth operational amplifier OP4 through the first zero and one switch S101. The positive output terminal of the four operational amplifiers OP4 is connected to the first zero-two switch S102, the first zero-two switch S102 is the output terminal of the amplifier, and is connected to the signal negative output terminal Von;

Among them, 6 groups of feedback switch resistor networks composed of switches and resistors in series are connected in parallel between the input terminal and output terminal of the first operational amplifier OP1, and the first group is composed of the second switch S21, the second resistor R2, the second two The switches S22 are connected in series; the second group is composed of the third first switch S31, the third resistor R3, and the third and second switches S32 in series; the third group is composed of the fourth first switch S41, the fourth resistor R4, and the fourth and second switches S42 in series ; The fourth group is composed of the fifth first switch S51, the fifth resistor R5, and the fifth second switch S52 in series; the fifth group is composed of the sixth first switch S61, the sixth resistor R6, and the sixth second switch S62 in series; the sixth group It is composed of the seventh first switch S71, the seventh resistor R7, and the seventh second switch S72 in series; the reverse first switch One end is connected between the eleventh switch S11 and the signal negative input terminal Vin, and the other end is connected between the twelfth switch S12 and the eighth first switch S81;

The first resistor R1, the first operational amplifier OP1 and the feedback switch resistor network form a resistor feedback programmable gain amplifier, the eleventh switch S11, the twelfth switch S12 and the reverse first switch Control the on-off of the programmable gain amplifier; when the eleventh switch S11 and the twelfth switch S12 are turned on, the gain expression of the programmable gain amplifier is as follows:

here is the voltage amplification factor of the programmable gain amplifier, is the resistance of the feedback switch resistor network, is the resistance value of the first resistor R1. It can be seen from the above formula that when When it remains unchanged, the gain can be changed only by changing the resistance value of the feedback switch resistor network, and the resistance value of the feedback switch resistor network can pass through the second first switch S21, the second second switch S22, the third first switch S31, and the third second switch. Switch S32, fourth first switch S41, fourth second switch S42, fifth first switch S51, fifth second switch S52, sixth first switch S61, sixth second switch S62, seventh first switch S71, seventh second switch S72 Control the on-off of the corresponding resistance to change.

The fixed-gain amplifier stage for coarse tuning includes a second operational amplifier OP2, a third operational amplifier OP3, a fourth operational amplifier OP4, an eighth-first switch S81, an eighth-second switch S82, and an inverting eighth switch , the ninth first switch S91, the ninth second switch S92 and the reverse ninth switch , the first zero-one switch S101, the first zero-two switch S102 and the reverse tenth switch .

reverse eighth switch One end is connected between the twelfth switch S12 and the eighth first switch S81, and the other end is connected between the eighth second switch S82 and the ninth first switch S91; the reverse ninth switch One end is connected between the eighth second switch S82 and the ninth first switch S91, and the other end is connected between the ninth second switch S92 and the first zero first switch S101; the reverse tenth switch One end is connected between the ninth and second switch S92 and the first zero-one switch S101, and the other end is connected between the first zero-two switch S102 and the signal negative output terminal Von.

The eighth first switch S81, the eighth second switch S82 and the reverse eighth switch Control the on-off of the second operational amplifier OP2, the ninth switch S91, the ninth second switch S92 and the reverse ninth switch Control the on-off of the third operational amplifier OP3, the first zero-one switch S101, the first zero-two switch S102 and the reverse tenth switch Controlling the on-off of the fourth operational amplifier OP4. By gating one or several stages of the three fixed-gain amplifier stages, different gains can be obtained to achieve the purpose of coarse gain adjustment.

Figure 3 shows the gain characteristic curve of the programmable gain amplifier with high gain accuracy in Figure 2. It can be seen that the programmable gain amplifier of the present invention can realize a gain adjustment range of 0~48dB, and the gain step size is 1dB.

Figure 4 shows the gain error curves of the programmable gain amplifier with high gain accuracy in Figure 2 at different gains. It can be seen that the gain error of the programmable gain amplifier shown in Figure 2 is very small under different gains, that is, the gain accuracy is very high.

In summary, the programmable gain amplifier with high gain accuracy proposed by the present invention has the advantages of high gain accuracy and simple gain control, and has broad application prospects in communication systems.

The above are only examples of the present invention, and do not constitute any limitation to the present invention. Obviously, under the thinking of the present invention, any skilled person who is familiar with the profession can use the technical content disclosed above without departing from the scope of the technical solution of the present invention. Appropriate adjustment or optimization of circuit structure and component size, according to the technology of the present invention refers to any simple modification, equivalent transformation and modification made to the above embodiments, all belong to the scope of the technical solution of the present invention.

Claims (2)

1. a programmable gain amplifier for high-gain precision, is characterized in that this amplifier carries out cascade by the accurately adjustable programmable gain amplifier level of gain and three fixed gain amplifier levels in order to coarse adjustment and formed; This amplifier circuit has the input of positive and negative two-way, exports, and this two-way circuit full symmetric designs, and wherein negative input, output signal processing circuit are:

In the programmable gain amplifier level that described gain is accurately adjustable, 11 switch (S11) is connected between signal negative input end (Vin) and the first resistance (R1) respectively, the reverse input end of another termination first operational amplifier (OP1) of the first resistance (R1), the positive output termination twelvemo of the first operational amplifier (OP1) closes (S12), the other end that twelvemo closes (S12) is output at the corresponding levels, the reverse input end of the second operational amplifier (OP2) is connect by the 81 switch (S81), second operational amplifier (OP2) positive output termination the eight or two switch (S82), the other end of the eight or two switch (S82) is output at the corresponding levels, the reverse input end of the 3rd operational amplifier (OP3) is connect by the 91 switch (S91), the positive output termination the 92 switch (S92) of the 3rd operational amplifier (OP3), the other end of the 92 switch (S92) is output at the corresponding levels, the reverse input end of four-operational amplifier (OP4) is connect by the one zero one switch (S101), the positive output termination the 1 switch (S102) of four-operational amplifier (OP4), one zero two switch (S102) is the output of this amplifier, connect signal negative output terminal (Von),

Wherein, between the input and output of the first operational amplifier (OP1), be connected in parallel 6 groups of feedback switch resistor networks be made up of switch and resistant series, first group is composed in series by the 21 switch (S21), the second resistance (R2), the two or two switch (S22); Second group is composed in series by the 31 switch (S31), the 3rd resistance (R3), the three or two switch (S32); 3rd group is composed in series by the 41 switch (S41), the 4th resistance (R4), the four or two switch (S42); 4th group is composed in series by switch on May Day (S51), the 5th resistance (R5), the five or two switch (S52); 5th group is composed in series by the 61 switch (S61), the 6th resistance (R6), the six or two switch (S62); 6th group is composed in series by the switch July 1st (S71), the 7th resistance (R7), the seven or two switch (S72); Reverse first switch ( ) an end be connected between the 11 switch (S11) and signal negative input end (Vin), the other end is connected on twelvemo and closes between (S12) and the 81 switch (S81); Reverse 8th switch ( ) an end be connected on twelvemo and close between (S12) and the 81 switch (S81), the other end is connected between the eight or two switch (S82) and the 91 switch (S91); Reverse 9th switch ( ) an end be connected between the eight or two switch (S82) and the 91 switch (S91), the other end is connected between the 92 switch (S92) and the one zero one switch (S101); Reverse tenth switch ( ) an end be connected between the 92 switch (S92) and the one zero one switch (S101), the other end is connected between the one zero two switch (S102) and signal negative output terminal (Von);

The 11 described switch (S11) all adopts cmos transmission gate circuit to the one zero two switch (S102), low level conducting; Described reverser adopts cmos transmission gate circuit, high level conducting;

Described the first operational amplifier (OP1) adopts two-stage calculation amplifier to add active degenerative structure, and first order operational amplifier wherein adopts Foldable cascade structure, and second level operational amplifier adopts the common-source stage structure of current source load; Feedback circuit produces the current source load end of corresponding feedback signal to second level operational amplifier according to output common mode signal and the difference of input reference voltage, thus adjustment output common mode signal, make it approach input reference voltage.

2. according to the programmable gain amplifier of high-gain precision according to claim 1, it is characterized in that described in order in the fixed gain amplifier level of coarse adjustment, second operational amplifier (OP2), the 3rd operational amplifier (OP3), four-operational amplifier (OP4) adopt the differential amplifier of band source degeneration resistance, be connected by resistance between the source class of differential pair input pipe, output adopts PMOS current source load, and the grid of PMOS is connected to difference output by two resistance.