JPS6129204A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To widen input and output dynamic range and to reduce the number of circuit elements by adding transistors to an amplifier circuit provided with a differential amplifier and a PP amplifier circuit. CONSTITUTION:Output V0 of the differential amplifier 11 drives a transistor TRQ15 that forms the PP amplifier circuit 12. Emitter current of the TRQ15 is supplied in common as base current of added TRQ16 and TRQ17. Voltage between base and emitter of the TRQ16 and forward voltage of a diode Q19 are impressed between bases of TRQ17, Q18. By adding this TRQ16, input dynamic range of the differential amplifier 11 can be enlarged without enlarging idling current of the PP circui 12. By utilizing between the base and emitter of the TRQ16, output dynamic range can be enlarged and the number of circuit elements can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an amplifier circuit suitable for use in various electronic devices.

[Background technology]

1969 IEEE International
l 5oljd-8tate C1rcvits Co
nference DIGESTOF TECHNI
CAL PAPER 8p16-p17 discloses an amplifier circuit using a current mirror circuit as a load of a first-stage differential amplifier and a complementary push-pull circuit at the subsequent stage.

When the present inventor studied the amplifier circuit disclosed in the above-mentioned document prior to the present invention, it was found that the pace current of the transistor Q11 flows into the collector of the transistor Q constituting the differential amplifier. The operating point of the dynamic amplifier is P, ~
It has been found that there is a large possibility that P. If the operating point changes to P, the amplification region with linearity decreases, which is undesirable.

Therefore, the present inventor developed an amplifier circuit having a circuit configuration as shown in FIG. That is, the transistors Q, to Q4, and the constant current circuit c's constitute a differential amplifier 1, and the transistor Qs is Darlington-connected.

Qs, further transistor Q, ~Qso*constant current circuit C
B constitutes a bushful circuit.

According to the above amplifier circuit, even when an idling current is passed through the transistor Q as an output signal of the differential amplifier 1 by the supply current circuit C8, the fluctuation in the operating point can be reduced.

Therefore, the input dynamic range is large and the idling current can be large, which also reduces crossover distortion as known to those skilled in the art.

However, when the inventor conducted further investigation, the maximum value of the output signal vout was Vcc-■cg, (sat)
-VBIiQ, vByo, -vByo, which turned out to be somewhat unsatisfactory when it was desired to widen the output dynamic range. Also, two diodes Q,,Q, are used as level shifters. It was noticed that there were problems in that the circuit elements were thick.

[Object of the Invention] The present invention corrects the above-mentioned problems, has good input dynamic range and output dynamic range, and has the following advantages:
An object of the present invention is to provide an amplifier circuit that can reduce the number of circuit elements.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief summary of the invention disclosed in this application is as follows.

That is, by providing the transistor Qss, the input dynamic range of the differential amplifier (transistors Q, □, Qt-) can be increased without increasing the idling current, and furthermore, by providing the transistor Qss, the input dynamic range can be increased by using a diode between the base and emitter of the transistor Qss. The purpose of the present invention is to increase the output dynamic range and to limit the number of circuit elements.

[Embodiment 1] Next, a first embodiment of an amplifier circuit to which the present invention is applied will be described with reference to FIG. Note that the amplifier circuit shown below is composed of a semiconductor integrated circuit (hereinafter referred to as IC),
The circles surrounding the numbers are external connection terminals.

The amplifier circuit shown in this embodiment commonly supplies the emitter current of the transistor Q111 to the transistors Qta+Qty, and utilizes the base-emitter voltage VB9.6 of the transistor Q1e to reduce the number of circuit elements. , which increases the input dynamic range and output dynamic range without increasing the idling current.

That is, as shown in FIG. 3, the circuit block 11 includes transistors Qll*Ql! connected in a differential pair. s
.

Transistor Qts*Q made into a current mirror circuit
14. The constant current circuit C8o constitutes an increase amplifier. Output voltage Vo corresponding to level change of input signal ■1n
is obtained, and drives the transistor Q□ forming the push-pull amplifier circuit 12.

What should be noted here is that the emitter current of transistor QCs is commonly supplied as a pace current to transistors Qxs and Qty, and the emitter current of transistor Q+a,
The voltage between z and V, the forward voltage between I and the diode Q1, and the voltage applied between the transistors Qi and Q5Qta. That is, the above VBEQ.

acts as a level shifter, and the number of level shifter diodes can be reduced accordingly.

Even if the idling current defined by the constant current circuit C8□ is made small, the transistor Qtv*Qt
A bias voltage can be applied between each pace of transistors Q1.・A small pace current is sufficient. As a result, there is no large difference in the collector current of the transistor QssvQ1t, and the offset voltage between each pace of the transistor Qll*Qu becomes small. Therefore, since the above-mentioned fluctuations in the operating point are reduced, the input dynamic range becomes equal to voltage.

On the other hand, the output signal ■. Maximum output of ut ■. utmax K
If you follow, 11voutmax = vcc VC
KQ4 (8at) VBEQ,.

Compared to the amplifier circuit shown in FIG. 2, the output dynamic range can be increased by 10 base-emitter voltages. This is very advantageous as an amplifier circuit with good power utilization when the +■cc power supply has a low voltage, and is suitable for downsizing electronic equipment. Note that C1 is an output capacitor and RL is a load.

[Embodiment 2] Next, a second embodiment of the present invention will be explained with reference to FIG. The difference between the amplifier circuit shown in this embodiment and the amplifier circuit shown in the first embodiment is that the transistor Qt+ is
The point is that the PN type transistor is replaced with a PNP type transistor Q, 1''.

Therefore, in the amplifier circuit shown in this embodiment, when the output voltage v0 is obtained, the transistor Q1;
K so that the base current is pushed to the collector of 1.

A trap, transistor Q1. Since the collector current of ' is commonly supplied to each base of the transistor QseyQst, the same circuit operation as described above is performed in the push-pull circuit 12, and the amount of the pace current may be extremely small. Therefore, fluctuations in the operating point as described above are reduced, and the input dynamic range can be increased in the same way as described above. In addition, as above, the output dynamic range can be increased and the number of elements in one circuit can be reduced.
Not only is it suitable for IC implementation, but it can also be used in electronic equipment that uses a low-voltage power supply.

[Embodiment 3] Next, a third embodiment of the present invention will be described with reference to FIG. 5.

As shown in FIG. 5, the amplifier circuit shown in this embodiment has P-channel MOS-FETs Q*t, Q□ connected to a differential pair, and a current mirror circuit (transistors Q, ,Q,).
The input side current of is configured to be able to be set independently of the input signal vin.

That is, the transistor Q is diode-connected, and the base and collector, which correspond to the cathode of the diode, are
It is connected to the pace of transistor Q, and is also connected to GNDK via resistor R1. Therefore, the input side current of the current mirror circuit, in other words, the current flowing through the transistor Qm, remains constant regardless of the input signals (2) and (n), and the output side current also corresponds to this. The base current of the transistor Ql11 operates in response to the input signal ■in by the operation of the MOS-FETs Q□ and Q□ connected to the differential pair.

Hereinafter, the circuit operation of the push-pull circuit shown in circuit block 12 operates as described in the first and second embodiments, and the effects as described in each of the above embodiments can be obtained.

〔effect〕

(1) By providing the transistor Qsa, a bias current can be supplied to the vertically connected output transistor without increasing the idling current of the push-pull circuit to a large current.

Pace-emitter voltage V of the above transistor QCs
By using B IQ, the number of circuit elements can be reduced.

(2) According to (1) above, transistor Qll+
A small pace current is required, and the input dynamic range can be increased by reducing fluctuations in the operating point of the differential amplifier.

13) According to 1) above, transistor Qra's ■
BEQ, 6 is irrespective of the output signal, and the output dynamic range can be increased accordingly.

(4) According to (31) above, the desired amplification operation can be performed even with a low power supply voltage.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the transistor Q18゜Q in each of the above embodiments
□ and may be replaced with P-channel MOS-FETs.

Furthermore, 'the above transistor Q 1 s is deleted, the transistor Q11 is directly connected to the power supply line, and the transistor Q11 is directly connected to the power supply line.
14 may be replaced with a resistor.

[Application field]

In the above description, the invention made by the present inventor was mainly explained with respect to the field of application, which is an amplification circuit, which is the background of the invention, but the invention is not limited thereto.

For example, it is suitable for electronic equipment that uses a low voltage power source, such as radio cassettes and double tape recorders.

The present invention is applicable to at least the commonly used linear IC.
It can be used for.

[Brief explanation of drawings]

FIG. 1 shows a characteristic diagram explaining variations in the operating point of a differential amplifier, FIG. 2 shows a circuit diagram of an amplifier circuit studied by the inventor prior to the present invention, and FIG. 4 shows a circuit diagram of an amplifier circuit showing a first embodiment of the present invention, FIG. 4 shows a circuit diagram of an amplifier circuit showing a second embodiment of the present invention, and FIG. 5 shows a circuit diagram of an amplifier circuit showing a third embodiment of the present invention. O showing the circuit diagram of Pl, P,... operating point, 11... circuit block showing differential amplifier circuit, 12... circuit block showing push-pull circuit, Q+t p Qst'? Qta +
Qts y QSs *Q1f, Q, 8...transistor, Qrs t Q! a...diode, cs,,
, cs, ... constant current circuit, ■, ... input signal n, v, out ... output signal. Figure 1 AA Figure 2/, 2 Figure 3 c Figure 4 IC3

Claims (1)

[Claims] 1. A signal to be amplified is supplied to the control terminal of the first transistor that forms part of the push-pull circuit and the control terminal of the second transistor that controls the idling current, and the voltage drop of the second transistor and this The control terminal of the first transistor and the third transistor vertically connected to the first transistor are controlled by the sum voltage of the voltage drop element provided in the current path of the second transistor. An amplifier circuit configured to apply a predetermined voltage between a terminal and a terminal.