JPS5848512A - Amplifying circuit - Google Patents

Abstract

PURPOSE:To make the integration of a circuit easy, by using an element of not high but low dielectric strength through the separation of the operating voltage source of the 1st and 2nd amplifying stages. CONSTITUTION:The 1st and 2nd current mirror circuits consist of transistors (TRs) Q8, Q9 and Q10, Q11. An output current of an output TRQ5 of the 1st amplifying stage 1 is converted into an output of the TRQ5. Further, this output current is converted into that of the TRQ11 and becomes an input driving current of the 2nd amplifying stage 2. Thus, operating voltage sources + or -V2, + or -V1 of the amplifying stages 1, 2 can be separated from each other. The amplifying stage 1 can be operated with the voltage + or -V2 lower than the operating voltage + or -V1 of the amplifying stage 2. Thus, the dielectric strength of each element can be small and the circuit integration can be made easy. Concretely, the prestage can be circuit-integrated by taking broken lines a-a' as a boundary.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit, and more particularly to an amplifier circuit having a plurality of amplification stages.

A general amplifier circuit consisting of a plurality of amplifier stages is the first one. As shown in the figure, the human input signal is connected to the differentially connected transistor Q
I I Q2- is current-converted by a constant current source 11 and active load current mirror transistors Q, , Q, and a differential amplifier which is a current amplification device. In addition, R, F
The human resistances R2 and R3 are the emitter resistances of the current mirror transistors Q, , Q, respectively.

This current output is the amplification transistor Q, which is the voltage amplification stage.
The voltage i is converted into voltage by 11, amplified, and outputted from its collector by a complementary pair of transistors q of one amplification stage in the next stage.

This becomes the base drive voltage of q. In addition, 1o is a transistor Q
,, A constant current source is provided secondly to generate the 4-s bias of the transistor Q, and to supply an operating current at a warm temperature of 10, for example, and El is the emitter voltage of the transistor Q. It is determined.

Both emitters of transistors Q, , Q7 are resistors R, , R.

It becomes the circuit output OUT through each of them, and drives a common load (not shown) in a low impedance nine push-pull manner. A capacitive element C is provided between the transistor Q and the collector for phase compensation, and a negative feedback circuit consisting of resistors R6 and R is used to control the circuit output and the transistor Q2 of the differential amplifier. It has the function of improving the circuit characteristics and maintaining the DC level at the circuit output point at zero potential.

In the circuit configuration shown in FIG. 1, the input stage differential amplifier (Q, , Q2) and voltage amplification stage (Q, ) are referred to as a first amplification stage 1, and the output power amplification stage (Q6, . . . ) is referred to as a first amplification stage 1. Q?) will be referred to as the second amplification stage.

In the above configuration, in order to increase the utilization rate of the power supply voltage (1), it is common to set the voltage drop in the resistor R3, the voltage loss in the constant current source I2, and the reference bias voltage E1 to be small. In this case, the collector potential of the transistor Q, which is the output active element of the first amplifier stage l, changes from a potential lower than the power supply voltage +■1 by El, to higher than the power supply voltage -■1 by the voltage loss of the current source I2. Since the voltage can swing up to the potential, the withstand voltage of the transistor Q is required to be approximately 2×v1. Therefore, transistors Q1 to Q5 and current source It
High breakdown voltage technology is required to integrate the first amplification stage 1 including T, but since there is a limit to increasing the breakdown voltage, it is significantly more expensive than when constructed using normal so-called discrete components. Performance will be degraded.

SUMMARY OF THE INVENTION An object of the present invention is to provide an amplifier circuit that does not require a high breakdown voltage and uses low breakdown voltage elements to facilitate circuit integration.

The amplifier circuit of the present invention has first and second amplification stages,
A current transfer means consisting of a current mirror is provided between these two to transfer the output current of the first amplification stage to the input terminal of the second amplification stage, and the operating voltage source of the first and second amplification stages is They are characterized by being able to be separated from each other.

The present invention will be explained below based on the drawings.

FIG. 2 is a circuit diagram of an embodiment of the present invention. Parts equivalent to those in FIG. 1 are designated by the same reference numerals. That is, current transfer means 3 consisting of a current mirror circuit is provided between the first and second amplification stages 1 and 20 outputs, and the operating voltage sources of both amplification stages 1 and 2 are separated from each other. To be more specific, the output amplification element of the first amplification stage 1 (PNP)
Converting the collector output current of transistor Q into the collector output current of transistor Q by a first current mirror circuit consisting of NPN) transistor Qs IQ,
Also, the collector output current of this transistor Q is PN
A second current mirror circuit including the P transistor QIQ t Qll converts the current into the collector output current of the transistor Q11. In addition, resistance R8~
R1i is each emitter resistance of each current mirror transistor Q8 to Ql+, and when the mirror ratio (current transfer ratio) is 1, /1iRs = RQ, Rto = , R
I, was selected. The collector output of the output transistor Qsi of the second current mirror circuit is used as the manual drive current for the second amplification stage, and this collector output point is the connection point between the pace of the output amplification element Q6 and the pipe circuit 10. It is connected to.

By doing this, the operating voltage sources of the first and second amplification stages can be separated from each other, and the operating voltage of the 11th amplification stage in the preceding stage is higher than the operating voltage ±V of the second amplification stage, which is the output stage. It can be operated at low voltage (2). for that,
The withstand voltage of each element is also small, and integration into an integrated circuit becomes extremely easy. Specifically, the front stage part can be made up of IC4 with respect to the broken line α-l in the figure, and the rear stage part can be constructed of discrete components with high withstand voltage.

In the example shown in Fig. 2, the input end transistor Q of the first current mirror circuit is a low voltage element and can be implemented as an IC, but the output side transistor Q needs to be a high voltage element and is a discrete component. 0 Therefore, the transistor Q,
and Q, the difference in vBE (pace-emitter voltage),
Due to the difference in the values of the resistors R8 and R9 and the difference in the temperature characteristics of these elements, the mirror ratio will not match the designed value, and the open loop gain and frequency characteristics of the amplifier circuit will change.

To avoid this drawback, a circuit according to another embodiment of the invention is obtained, as shown in FIG. In FIG. 3, the same parts as in FIGS. 1 and 2 are given the same reference numerals, and the output of the first current mirror circuit consisting of transistors Q, Q, and the second current mirror circuit consisting of transistors Q1゜s Qtt are shown. A pace-grounded NPN transistor Q+2 is connected in cascode and inserted between the current mirror circuit and the current mirror circuit. By doing this, transistors Q and Q10 perform a so-called cascode operation, and the collector potential of transistor Q is clamped to a substantially constant value (zero volts), making transistor Q lower than in the case shown in FIG. Since transistor Q0 can be used as a voltage-resistant element, transistor Q0 can be integrated into an IC on the same chip as transistor Q, so characteristics can be made uniform, and the mirror ratio of the first current mirror circuit is It is possible to follow the design, resulting in stabilization of the circuit.

In addition, in the circuits shown in Figs. 2 and 3, in order to obtain the same frequency characteristics as the circuit shown in Fig. 1, the phase compensation capacitor C
8 must be chosen more favorably than in the circuit of FIG.
By connecting a capacitor C1 between the pace of transistor Q6 and the pace of transistor Q6, the same frequency characteristics can be obtained with the same capacitance as in the circuit of FIG. Also, transistor Q
A capacitor CI may be provided between the pace of , and the circuit output OUT.

FIG. 4 is a circuit diagram of another embodiment of the present invention, in which parts equivalent to those in FIGS. 1 to 3 are designated by the same reference numerals. To describe only the parts that are different from the above-mentioned sides, the manual differential amplifier stage of the first amplification stage l is composed of FETs (field effect transistors) Q, , Q2, and each transistor Q, , Q2 and a transistor QCs * Q10
is considered to be a cascode amplifier type. Note that the resistor R1 and the current source 11. I, the pace potential of the transistors Q13 and sQ4' is kept constant and both transistors are operated in a grounded mode. The load of the Kakudo amplifier is a resistive load made up of resistors R1, 3, R, , and between both loads there is a resistor R17 and a capacitor C2.
and are connected in series.

The outputs derived from the collector loads R1, 8, and R are input to the second differential amplifier. This amplifier consists of a differential transistor Q+5 + Q16 + a current source I4 and a load resistor R, 5, R, 9, both ends of a resistor R16.
) Ranjistor Q, pace human power is taken out.

A cascode amplifier is configured by transistor Q and transistor Qta, and is intended to improve characteristics. still,
R2 is the pace node of the transistor Qta (Iasumi Shobara), and a phase compensation capacitor C1 is connected between the pace of the transistor Q and the collector of the transistor QCs.
is inserted. The collector output of this transistor Q+8 is the snoring transistor Q,,Q.

It serves as an input terminal of a first current mirror circuit consisting of the following, and current is transferred to the next stage amplification section 2. After that, the third
It has the same configuration as the circuit example in the figure, and its explanation will be omitted.

This example also has the advantage that the first voltage amplification stage 1 and the first current mirror circuit can be integrated into an IC on the same chip.

As described in the paper, according to the present invention, the pre-stage amplifier section can be operated with a low power supply, so it can be constructed from low-voltage elements, and it is therefore extremely easy to integrate it into an IC.

The maximum output of the entire amplifier circuit is determined by the circuit connected to the subsequent stage and its power supply voltage, so the front stage has versatility and can be used in a wide range of amplifiers, from low output amplifiers to medium and small output amplifiers. become.

Note that a part of the Bibo 2 elements described above can be replaced with other active elements such as FET elements.

[Brief explanation of drawings]

Figure 1 shows an example of a conventional amplifier circuit, Figures 2 and 3.
4 and 4 are circuit diagrams showing embodiments of the present invention, respectively. Explanation of symbols of main parts l...First amplification stage 2...Second amplification stage 3.
... Current transfer circuit Q, ... Voltage amplification transistor Q, , Q, ... Power amplification transistor Qa +
Q9 t Qto + Q+'+... Current mirror transistor applicant Pioneer Co., Ltd. agent Patent attorney Motohiko Fujimura / [21 Figure 3

Claims (6)

[Claims] (1) An amplifier circuit comprising a first amplifying means and a second amplifying means for further amplifying the amplified output, the amplifying circuit comprising:
An amplifier circuit comprising current transfer means for transferring the output current of the amplification means to the input of the second amplification means, the operating voltage sources of the first and second amplification means being separated. . (2) The current transfer means includes a first current mirror circuit which receives the output current of the first amplification means and includes an active element of a conductivity type opposite to the output active element of the first amplification means; A second current mirror circuit which receives the output current of the first current mirror circuit and is made of an active element of the same conductivity type as the output active element.
2. The amplifier circuit according to claim 1, further comprising a current mirror circuit, wherein the output current of the second current mirror circuit is used as the manual power of the second amplifying means. (3) The output of the first current mirror circuit and the second current mirror circuit
Claim 2, characterized in that a common base type cascode transistor connected in cascode to the output transistor of the first current mirror circuit is provided between the current mirror circuit and the human power. The amplifier circuit described. (4) The operating voltage source of the first amplifying means has a lower voltage than that of the second amplifying means. Amplification circuit. (5) The amplifier circuit according to claim 4, wherein the first amplifying means is an integrated circuit. (6) The amplifier circuit according to claim 3, wherein the first amplifying means and the first current mirror circuit are integrated circuits.