GB2030805A - Current sources - Google Patents

Abstract

A stabilized current sources network for an LSI circuit comprises n multiple collector transistors (11... 1n) each having m collectors connected to respective electronic elements (2), one collector of any one transistor being coupled via a load resistor (9) to a bus (10), and includes a stabilization unit (3) comprising a reference voltage source (4), an amplifier (6), and a comparator (5) all connected substantially as shown. The unit (3) stabilises the current through the said one collector, and the currents through the other collectors are coupled thereto by current mirror action. <IMAGE>

Description

SPECIFICATION Stabilized current sources network The invention relates to communication electronics, and more particularly to a stabilized current sources network.

The invention is suitable, in the form of stabilized current sources, for use with integrated circuits employed in computer, measurement, radar and pulsed-technique industries.

There is disclosed a stabilized current sources network comprising transistors having their bases coupled to a stabilization unit, and having their collectors coupled to electronic elements, said transistors being implemented, according to the invention, in the form of n multiple collector transistors each having m collectors, one of said m collectors of any one of said n multiple collector transistors being coupled to a first lead of a load resistor having its second lead coupled to a first common bus, a stabilization unit having a reference voltage source, an amplifier and a comparison unit which has a first input coupled to the output of the reference voltage source, and has a second input coupled to the first lead of the load resistor, the output of the comparison unit being coupled to the input of the amplifier, and the output of the amplifier being coupled to the bases of the n multiple collector transistors having their emitters coupled to a second common bus.

The invention therefore makes it possible to realize LSI circuits having a large degree of integration, which provides, for example, for a greater performance of computers.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a block diagram of a stabilized current sources network, according to the invention; Figure 2 is a circuit diagram of the stabilization unit, according to the invention.

The stabilized current sources network of the invention comprises current sources built around n multiple collector transistors it... 1 (Fig. 1) each having m collectors coupled to electronic elements 2, and a stabilization unit 3. The latter incorporates a reference voltage source 4, a comparison unit 5, and an amplifier 6. An input 7 of the comparison unit 5 is coupled to the output of the reference voltage source 4, while an input 8 of the comparison unit 5 is coupled to a first lead of a load resistor 9. Connected to the first lead of the load resistor 9 is one of the m collectors of any one of the n multiple collec tor transistors 11 . 1 n' A second lead of the load resistor 9 is coupled to a common bus 1 0. The output of the comparison unit 5 is coupled to the input of the amplifier 6.An output 11 of the amplifier 6 is connected to the bases of the n multiple collector transis tors 1, . 1, n having their emitters coupled to a common bus 12.

Fig. 2 illustrates a circuit diagram of the stabilization unit 3, incorporating resistors 13, 14; stages for biasing the input voltage level, built around emitter followers, the first one of the latter employing a transistor 1 5 and a resistor 16, and the second employing a transistor 1 7 and a resistor 18; a differential amplifier designed to compare voltages applied to it and perform voltage amplification and built around transistors 19, 20 and resistors 21, 22; and a current amplifier which is a third emitter follower employing a transistor 23 and a resistor 24. The resistors 13, 14 are connected in series, while the resistor 1 3 is coupled to the common bus 10 and the resistor 1 4 is coupled to the common bus 1 2.

The connection point of the resistors 13, 14 is connected to the base of the transistor 1 5 having its collector coupled to the common bus 10, and having its emitter coupled to the base of the transistor 20 and, via the resistor 16, to the common bus 12. The emitter of the transistor 20 is coupled to the emitter of the transistor 19 and, via the resistor 21, to the common bus 1 2. The collector of the transistor 20 is coupled to the base of the transistor 23 and, via the resistor 22, to the common bus 10.

The collector of the transistor 1 9 is coupled to the common bus 10, while the base of the transistor 1 9 is coupled to the emitter of the transistor 1 7 and, via the resistor 18, to the common bus 1 2. The transistor 1 7 has its collector coupled to the common bus 10, and has its base coupled to one of the m collectors of any one of the n multiple collector transistors 1, . . .1 n (Fig. 1) and, via the load resistor 9, to the common bus 10. The transistor 23 (Fig. 2) has its collector coupled to the common bus 10, and has its emitter coupled to the bases of the n multiple collector transistors 1i . .. n (Fig. 1) and, via the resistor 24 (Fig. 2) to the common bus 1 2.

The reference voltage source 4 (Fig. 1) is built around the resistors 13, 1 4. The comparison unit 5 (Fig. 1) is built around the transistors 1 5 (Fig. 2), 17, 1 9, 20 and the resistors 16, 18, 21, 22. The amplifier 6 is built around the transistors 1 9 (Fig. 2), 20, 23 and the resistors 21, 22, 24.

The network of the invention operates in the following manner. The currents through the stabilized current sources are determined by the voltage produced by the reference voltage source 4 (Fig. 1). This voltage is applied to the input 7 of the comparison unit 5. Applied to the input 8 of the comparison unit 5 is the voltage across the load resistor 9.

Since the current gain p, of the n multiple collector transistors 1, . . 1., the temperature and the power supply tend to vary, the voltage across the load resistor 9 is subject to a variation (the latter voltage becomes less or more than the voltage available from the reference voltage source 4) and an error signal appears at the output of the comparison unit 5 which is amplified in the amplifier 6 and is passed to the bases of the n multiple collector transistors 11... 1 with the result that the voltage across the load resistor 9 is increased or decreased. The appearance of the voltage proportional to the current through the load resistor 9 and equal to the voltage of the reference voltage source 4 causes the error signal at the output of the comparison unit 5 to assume zero.In this case, the current through the current source employing the multiple collector transistor 1 n assumes a value proportional to the voltage produced by the reference voltage source 4. On the other hand, the currents through the current sources employing n - 1 multiple collector transistors 1, . . .1 1nazi assume their values proportional to the current through the load resistor 9 due to the fact that the parameters of these transistors, as belonging to integrated circuits, are identical.

The employment of the multiple collector transistors makes it possible to replace four current sources comprised of eight components and occupying four insulated regions in the integrated circuits with a single multiple collector transistor which requires no insulated region. This therefore provides for a greater degree of integration of LSI circuits.

The temperature variation as well as the identical variations of the parameters of the transistors 1 5 (Fig. 2), 17, 19, 20, 23 and the n multiple collector transistors 1, . . .1 1 (Fig. 1), at a large gain K of the amplifier 6 and at a small output impedance of the latter, do not practically cause a change in the currents through the stabilized current sources since these variations are decreased in value by a factor of K due to the operation of the amplifier 6. Thus, the network of the invention provides for a greater degree of integration of the LSI circuits and improves the stability of the current sources.

Given below is a detailed description of the operation of the stabilization unit 3 (Fig. 2).

The voltage across the connection point of the resistors 1 3, 1 4 is applied to the input of the first emitter follower built around the transistor 1 5 and the resistor 1 6. This voltage does not practically depend on the temperature variation. The output of the first emitter follower produces a voltage applied to the first input of the differential amplifier built around the transistors 19, 20 and the resistors 21, 22. The voltage across the load resistor 9 (Fig. 1) is applied to the input of the second emitter follower built around the transistor 1 7 (Fig. 2) and the resistor 1 8. The voltage obtainable from the output of the second emitter follower is applied to the second input of the differential amplifier.The emitter followers connected to the inputs of the differential amplifier make it possible to increase its voltage gain and to extend the linear portion of its transfer characteristic so that this linear portion does not lie in the saturation region for a wide range of variation of destabilizing factors. The differential amplifier operates to compare the voltages applied to it and to perform voltage amplification.

The resistors 21, 22 help select the operating mode and the gain of the differential amplifier. The output voltage of the latter is applied to the input of the third emitter follower built around the transistor 23 and the resistor 24. The output of the third emitter follower produces a voltage applied to the bases of the n multiple collector transistors 1, . . . 1 n (Fig. 1). The third emitter follower is responsible for a small output impedance of the differential amplifier. As a result, a variation in the gains of the n multiple collector transistors 1, . . n does not give a considerable influence on a variation of the currents through the stabilized current sources employing these transistors.

The stabilization unit 3 has a large gain, a small output impedance and a high loading capability. The output of the stabilization unit 3 can be connected to the multiple collector transistors 1, . . . 1n as a maximum, which corresponds to 40 current sources. With the stabilization unit 3, the current sources can be stabilized as the transistor parameters and the temperature tend to vary on a wide basis.

The invention therefore provides for a smaller number of components and insulated regions of LSI circuits and for greater stability of the associated current sources.

Claims (2)

1. A stabilized current sources network comprising transistors having their bases coupled to a stabilization unit, and having their collectors coupled to electronic elements, said transistors being implemented in the form of n multiple collector transistors each having m collectors, one of said m collectors of any one of said n multiple collector transistors being coupled to a first lead of a load resistor having its second lead coupled to a first common bus, a stabilization unit having a reference voltage source, an amplifier, and a comparison unit which has a first input coupled to the output of the reference voltage source and has a second input coupled to the first lead of the load resistor, the output of the comparison unit being coupled to the input of the amplifier, and the output of the amplifier being coupled to the bases of the n multiple collector transistors having their emitters couplet to a second common bus.

2. A stabilized current sources network substantially as hereinbefore described with reference to the accompanying drawings.