JPS6098708A - Low frequency amplifier circuit - Google Patents

Abstract

PURPOSE:To decrease the current change due to temperature drift by driving a buffer stage and an output stage amplifier with an output of a comparator so as to allow the switching operation of the amplifier. CONSTITUTION:Since a DC voltage from a positive power supply +Vcc is impressed to a point A at no signal while being divided by fixed resistors R1 and R2, when a voltage at a point B is lower than the voltage at a point A, an output of a comparator Q1 is a high potential, transistors Q2, Q4 are turned on, Q3, Q5 are turned off and a point B becomes a high potential. Thus, the input side potential of the Q1 is increased gradually via an LPF consisting of a fixed resistor R3 and a capacitor C2. Since the potential is higher than that at the point A at a certain point of time, the output of the Q1 goes to a low potential, the Q3, Q5 are turned on and then the Q2, Q4 are turned off, and the potential at the point B goes to a low potential. This potential is applied to the Q1 via the LPF comprising the C2, R3. The operation above is repeated and the potential at the point B is switched at high speed around the potential at the point A.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low frequency amplifier circuit that performs a switching operation using high frequencies.

In conventional low frequency amplifier circuits, up to the drive stage is
class amplification, and the output stage was a class AB amplification stage, but the bias circuit of the class AB amplification in the output stage tends to cause the idle current to become unstable due to fluctuations in temperature and power supply voltage, and also causes crossover distortion. Ta.

The present invention G1 has been developed to eliminate such drawbacks of the conventional art, and embodiments thereof will be described below in detail with reference to the drawings.

FIG. 1 shows the basic circuit of the low frequency amplifier circuit of the present invention, in which the input signal terminal is connected to the Φ input terminal of comparator Q1 via capacitor 01, and the comparator Qs
and transistor Q2. Three complementary amplifiers and transistors. 4 and a complementary amplifier called Q5 are connected in cascade.

The former amplifier is used as a drive stage, and the latter amplifier is used as an output stage. Fixed resistors R1 and R2 are connected to the connection point between the capacitor C1 and the input terminal of the comparator Q1,
The other end of the fixed resistor R1 is connected to an I4 source, and the other end of the fixed resistor R2 is grounded.

On the other hand, the output side (2) connected between the emitters of transistors Q4 and Q6 is connected in cascade with a chiroke coil L and a capacitor C3, and the other end of the capacitor C3 is connected to the input terminal of the speaker SP at a connection point O. From the 0 connection point (2), which grounds the other end terminal of the speaker SP, connect it to the e terminal of the control Qs via a low-pass filter consisting of a fixed resistor, capacitor c, and J. In the circuit configured as above, the DC power supply +vcc is connected to fixed resistors R1 and R
A DC voltage divided by 2 is applied to the ■ terminal of commutator Q1, and transistors Q2 and QS
The drive stage combining transistors Q4 and Qs and the output stage combining transistors Q4 and Qs both operate at zero bias. Therefore, a loop circuit is formed such as comparator Q1 → drive stage Qz Qs → output stage Q4 Q8 → low-pass filter R3C, and when a signal input arrives, the signal input activates the input signal SP. In this case, the DC voltage from the power supply +vcc is applied to the 0 point after being divided by the fixed resistors R1 and 82, so if the voltage at the 0 point is lower than the voltage at the point, the converter Q
The output of 1 becomes a high potential, transistors Q2 and Q4 are turned on, transistors Qs and Qs are turned off, and the 0 point is still at a potential, so the low-power filter RaC
The potential on the input side of the controller Q1 also gradually increases through z(i=.

At the point of 6, the [stock] point will be higher, so con 7 or rate Q! The output of transistors Q3 and Q becomes a low potential.
S turns on and the transistor turns on. 2 and Q4 are turned off, and about % of the 0 point becomes a low potential.

This position is applied to the comparator Ql via the low-pass filter R3C.

By repeating this operation, the potential at the 0 point is switched at high speed around the potential at the 0 point.

Therefore, the signal input is predicted - Cu coil L and capacitor Cm
'If you apply it to the speaker SP via fc, the high frequency component will be removed and only the low frequency component will be added. In this case, the output will be zero unless the 4m human power is applied, so the signal is input to the point via the 1 capacitor C1. If you give
output to the point.

In the basic circuit shown in FIG. 1, only a switching operation is performed and the voltage is not amplified.

FIG. 2 shows an embodiment in which an amplification action is added in addition to the switching operation in FIG. 1.

That is, a fixed resistor R is inserted between the e input terminals of the comparator Ql and the fixed resistor R1 in FIG. 1, and a fixed resistor R4 is inserted in parallel between the e input terminals and the e input terminals of the comparator intervene.

In this case, the voltage amplification factor is β=Sat.

4. Fig. 3 is an actual example in which a control circuit is provided in the basic circuit shown in Fig. 1, and a transistor is connected between the fixed resistor R2 provided at the Φ input terminals of the commutator Q1 and the ground. Qs' is arranged so that a control input is supplied to the pace side via a fixed resistor R6.

Normally, when a voltage is applied to the control input, on/off operations are performed in the same way as the embodiment shown in FIG.

When the control input is set to ground, transistor Q6 has a power,
When the current is turned off, the current that was flowing through the fixed resistors R1, R2 and the transistor Q6 no longer flows, and the voltage drop across the fixed resistor R1 becomes zero, so the potential at the point is αcc.
becomes the same potential as

Therefore, the output side of the comparator Qt becomes a high potential, and the transistors Q2 and Q4 are turned on, and e input terminals of the comparator Ql become a high potential through the low pass filter Rs Cm t-. However, since there is a voltage drop between transistors Q2 and Q4, the potential of e input terminals of comparator Q1 is high by that amount, and comparator Ql
The output of is held and the operation is stopped. The power consumption at this time is only the circuit current of the converter Ql and is extremely small. It is also effective when used as squelch signal control for wireless communication equipment.

As described in detail above, according to the present invention, it is possible to provide a low frequency amplification circuit that has low component costs, eliminates the trouble of circuit adjustment, and has little current change due to temperature drift.

[Brief explanation of the drawing]

FIG. 131 is a wiring diagram of a low frequency amplifier circuit showing one embodiment of the present invention, and FIGS. 2 and 3 are wiring diagrams of a low frequency amplifier circuit showing other embodiments of the invention. Q!・・・Kono Mother Reta, Qz r Qs + Q4
r Qs *Q6...Transistor, R1r R2
, R3r R4rR5* R6-solid mouse resistance, C1r C
2r Ca * C4+C6...Capacitor, L...
・Choke coil, SP...Speaker. Patent applicant Yaesu Musen Co., Ltd.

Claims (1)

[Claims] One or two stages of zero-bias complementary amplifiers are cascaded and connected as an output stage or a buffer stage and an output stage, and a part of this low frequency output is passed through a low-frequency filter to one of the comparators. The signal input is connected to the input terminal of the comparator, and the signal input is connected to the other input terminal of the comparator, and the output of the comparator drives the buffer stage and the output stage amplifier, thereby performing switching operation at a high frequency. A low frequency amplification circuit with all the following features.