JPS6043682B2 - signal amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal amplifier using a differential amplifier, and in particular to an acoustic amplifier suitable for integrated circuits.

FIG. 1 is a basic configuration diagram of a conventionally well-known differential input acoustic amplification integrated circuit, in which an input signal is applied via input terminal 1 to an amplifier 12 whose input stage is a differential amplifier, and from output terminal 2. I was getting output.

The bias of the input terminal 1 is determined by a leader circuit including resistors 6 and 7, and the capacitor 41 is an external ripple filter capacitor provided to prevent power supply ripple from affecting the input. The negative feedback circuit is constructed from the output terminal 2, resistors 9 and 10, and an external capacitor 11. The differential input acoustic amplifier with the above circuit configuration requires capacitors 11 and 41, and these capacitors must have a large capacity in order to lower the AC impedance. When creating a circuit, this capacitor had to be an external component. An object of the present invention is to obtain a signal amplifier using a differential amplifier that can configure an integrated circuit with at least four terminals by removing the capacitors 11 and 41. According to the present invention, a differential input amplifier receives an input signal at a non-inverting input terminal, a plurality of resistors are connected in series between power lines that apply a bias potential to the non-inverting input terminal, and an output of the differential input amplifier. A feedback resistor connected between the terminal and the inverting input terminal, a resistor for setting the amount of negative feedback with one end connected to the inverting input terminal, and a bias potential given to the non-inverting input terminal are input, and the output is set to negative feedback. A signal amplifier having an in-phase amplifier with a gain of ``1'' applied to the other end of the resistance for setting the quantity is obtained.

Next, one embodiment of the present invention will be described using FIG. 2.

The same reference numerals are used for the same parts as in the differential input acoustic amplifier in FIG. A bias is applied from the middle point of the reader circuit connected between 3 and the common terminal 4 via a resistor 8, and an input signal is applied from the input terminal 1.

On the other hand, the output terminal 2 is connected to an inverted non-input terminal (feedback input terminal) via a resistor 10, and a signal at the connection point of the resistors 6, 7, and 8 is connected to this inverting input terminal via a resistor 9. The output of an in-phase amplifier 13 with a gain of 1 is added to the input. If the output impedance of the common-mode amplifier 13 with a gain of 1 is ZO, and the resistance values of the resistors 9 and 10 are R9 and RlO, then the return rate is (ZO+R9)/(
ZO+R9+RlO), but ZO can be almost ignored.

It is also possible to determine the return rate by considering R9 and RO. The effect of the differential input acoustic amplifier 13 on the power supply ripple is that the power supply ripple at the output end of the leader circuit is applied to the input terminal 1, and at the same time, it is applied to the negative feedback input terminal via the common mode amplifier 13 with a gain of 1 and the resistor 9. Input terminal 1
The power supply ripple that appears in is canceled out.

Therefore, in semiconductor integrated circuits, external capacitor 1
It is a great advantage to remove 1 and 41 and replace them with transistors and resistors to create an integrated circuit. Next, a specific embodiment of the present invention will be described using FIG.

An input bias is determined from a leader circuit of resistors 6 and 7 via a resistor 8, and a differential circuit 21 is used as an input, and a polarity-inverted driver. into the PNP transistor 24 for the drive, and the phase compensation (oscillation prevention) capacitor 4
0 is connected between the base and collector of the transistor 24,
The collector of the drive transistor 24 is connected to the bases of the final stage NPN Darlington connection transistors 26 and 27, and from the collector of the transistor 24, the final stage PNP Darlington connection transistor 28, The final stage is a complementary circuit consisting of NPN and PNP transistors. The transistor 23 and the resistor 15 are constant current sources of the differential circuit, and the constant voltage source (the resistor 16
and diodes 33, 34), the transistor 25 and resistor 17 determine the idling current, the diode chain is the final stage bias circuit, and the resistors 9, 10
is a negative feedback circuit, which enters the negative feedback input of the differential circuit 21 from the output terminal 2 via the resistor 10. Leader circuit (resistor 6,
7) In-phase amplifier differential circuit 22 with a gain of 1 from the output terminal of
It enters the non-inverting input terminal of
The base of transistor 32 is connected to
0 is connected to the base of the final stage NPN transistor 31 via diode chains 38 and 39,
The final stage is NPN, . This is a complementary circuit of PNP transistors, and the output terminal of this complementary circuit is fully fed back to the inverting input of the differential circuit. The resistor 18 is
In the constant current source of the differential circuit 19, the resistor 20 is a constant current source for determining the idling current, and the diodes 38 and 39 are the final stage bias circuit. An acoustic amplifier equipped with a negative feedback circuit can be realized using only input/output terminals, and when integrated into a semiconductor integrated circuit, no external elements are required, making it possible to obtain an integrated circuit that is extremely easy to handle.

Further, at this time, the semiconductor chip does not require terminals for external components, which not only reduces the occupied area, but also allows the container to be made with four terminals, making it extremely inexpensive to form. Furthermore, since the number of wire bondings connecting the electrodes on the semiconductor chip and the electrodes of the container is small, it is possible to obtain a semiconductor integrated circuit with good reliability and yield.

[Brief explanation of drawings]

FIG. 1 is a basic circuit diagram of a conventional differential input amplifier. FIG. 2 is a basic circuit diagram of an embodiment according to the present invention.
FIG. 3 is a circuit diagram of a specific embodiment using the present invention. 1...Input terminal, 2...Output terminal 3
...Power terminal, 4...Common terminal, 5...
... Negative feedback input terminal, 21, 22 ... Differential circuit, 6, 7, 8, 9, 10, 14, 15, 16, 17,
18, 19, 20...resistance, 11, 41, 40...
Capacitor, 33, 34, 35, 36, 37, 38,
39...Diode, 23, 24, 25, 26
, 27, 28, 29, 30, 31, 32...transistor, 12...differential input acoustic amplifier, 1
3... Common mode amplifier with a gain of 1.

Claims (1)

[Claims] 1. A differential input amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal; a plurality of resistors connected in series between power supply lines to obtain a bias potential for the non-inverting input terminal at an intermediate connection point; means for applying a bias potential obtained at the intermediate connection point to the non-inverting input terminal, a first negative feedback resistor connected between the output terminal and the inverting input terminal, and one end of which is connected to the inverting input terminal; a second negative feedback resistor connected to the in-phase amplifier; A signal amplifier comprising a signal input terminal connected to the non-inverting input terminal and a signal output terminal connected to the output terminal.