JPS5991710A - Amplifier circuit - Google Patents

Abstract

PURPOSE:To attain ease of circuit integration by forming a circuit not requiring any input coupling capacitor and any bypass capacitor. CONSTITUTION:A PNP transistor (TR) Q4 connected to a signal source 6 is connected to an NPN TRQ1 and a constant current source 8 via a diode D3. Further, a PNP TRQ5 connected to a resistor R2 is connected to an NPN TRQ2 and a constant current source 9 via a diode D4. Further, each emitter of the TRQ1, Q2 forming a differential amplifier is connected to a constant current source 10. Moreover, a negative feedback circuit network 7 is connected to an output of an amplifier A of the post-stage via an output coupling capacitor C3, and a resistor R3 is connected between the output of the amplifier A and the base of the TRQ2. Thus, neither input coupling capacitor nor bypass capacitor is required in this way, allowing to attain ease of circuit integration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an amplifier circuit, and is particularly suitable for integration into an integrated circuit.

[Prior art]

As an example of a conventional amplifier, an audio preamplifier circuit is shown in FIG.

In FIG. 1, l is an input terminal, 2 is a negative feedback terminal, 3 is an output terminal, and 4 is a power supply terminal. Transistor Qll
02 have their emitters connected to each other and are also connected to the collector of the constant current transistor Q3. In addition, a constant current source 5 and a diode group DI are connected in series to the power supply and the ground plane.
+D From the connection point of 2, resistor R1 connects to transistor Q
Connected to the base of 1. Further, a signal (6) is connected to the base of Ql via an input coupling capacitor CI.

On the other hand, the base of transistor Q2 is grounded through a series circuit of resistor R2 and capacitor C2. A load Zl is applied to the collectors of transistors Q and Q2, respectively.
, Z2 are connected to the amplifier A at the subsequent stage. A resistor R3 is connected between the output of the amplifier A and the base of the transistor Q2, and a negative feedback network 7 is connected through an output coupling capacitor c3. R4
is the load resistance.

Next, the operation of this conventional example will be explained.

A signal applied from the signal source 6 via the input coupling capacitor c1 is amplified by the first-stage differential amplifier Qll02, outputted to each collector, and further amplified by the subsequent-stage amplifier A. A part of the output signal is subjected to AC negative feedback by negative feedback network 7 and resistor R2, and the voltage gain is determined by the ratio of the combined impedance of this network 7 and resistor R3 to the resistor R2. This negative feedback stabilizes the gain, improves the distortion rate, and provides equalizer frequency characteristics in this example.

Further, the output bias is stabilized by negative DC feedback using resistors 1 to 3.

However, in the amplifier circuit shown in this conventional example, the input coupling capacitor C1 and the negative feedback bypass capacitor C2
Requires. Therefore, since the above capacitor has two time constants, the difference voltage is amplified due to the slight difference in the rise of the power terminal 1 and the negative feedback terminal 2 when the tli source is turned on.
In this loop, the voltage at the output terminal 8 fluctuates greatly, the fluctuation is fed back to the negative feedback terminal, and the output fluctuates further.
There are many cases where the voltage at the output terminal wavers transiently when the power is turned on. In the case of these audio amplifiers, so-called shock noise is generated from the speaker through the power amplifier that is later turned on, so it is necessary to take measures such as shock noise prevention circuits, such as making the rise and fall of the voltage at the output terminal gradual. Causes problems.

Furthermore, since the capacitance values of these two capacitors are relatively large, when integrated into a circuit, they have the disadvantage of increasing the number of external parts.

[Summary of the invention]

In order to solve the above-mentioned drawbacks, the present invention provides an amplifier circuit that does not require a manual coupling capacitor or a bypass capacitor.

[Embodiments of the invention]

The present invention will be explained below.

FIG. 2 is an embodiment of the present invention. Note that the same or corresponding parts as in FIG. 1 are indicated by the same reference numerals.

i'NP) The collector of the transistor Q4 is grounded and its base is connected to the signal source 6 of the input terminal 1.

The cathode of the diode D3 is connected to the emitter of the transistor Q4, and the anode is connected to the base of the npn transistor Q1 and to the power supply via the constant current source 8. Also PNP) transistor Q,
The collector is grounded, and the base is grounded from the negative feedback terminal 2 through a resistor R2. The cathode of the diode D4 is connected to the emitter of the transistor Q, and the anode is connected to the base of the NPN transistor Q2, and is also connected to the power supply via the constant current source 9. The above npn transistor QL constituting a differential amplifier,
The emitters of Q2 are connected to each other and grounded via a constant current source 9. The negative feedback network 7 is connected between the output of the rear stage amplifier A and the negative feedback terminal 2 via an output coupling capacitor C3. Further, a resistor R3 is connected between the output of the latter stage amplifier A and the base of the transistor Q2.

Next, the operation of this embodiment circuit will be explained.

The input signal applied by the signal source 6 reaches the base of the npn transistor Q1 via the emitter follower transistor Q4 and the level shifting diode D3, and
An amplified output is obtained at the collector of the L transistor Q1. It is further amplified by a subsequent stage amplifier A, and is obtained as an output by a load resistor 1. The negative feedback is provided by the negative feedback network 7 and the resistor R3G.

Next, the voltage gain of this example is determined.

In general, negative feedback amplifier IT! , the pressure gain Gv is given by the following equation, where An is the open circuit gain and β is the feedback factor, and when An > 1.

O ■ β In the case of this embodiment, if the impedance of the negative feedback circuit M87 is the dynamic resistance of the Z diode, the voltage gain is determined by the following equation.

1i R2(R,++r)-1-R2Z7R2
Z7+R3+r R2R4 3 in 10 This result is equal to the value of the conventional example shown in FIG.

Next, in order to suppress the offset of the DC voltage of the output terminal 3 in this embodiment, the following measures are taken.

That is, the outputs of constant current sources 8 and 9 [current 10] are set to the same value, and the resistance value of R3 is approximately equal to the current resistance Rg of the input signal source (set to +i''1. In order to keep it low, DC feedback is applied from the output terminal 8 to the base of the transistor Q2 with a resistor R3.Here, the current I flowing through the signal source resistor Rg and the resistor 1<2 is as follows: When , the voltage drop across the resistor becomes approximately zero, making direct connection possible without using a coupling capacitor or a bypass capacitor.

Note that the diode in the above embodiment may be one in which the collector base of a transistor is short-circuited, and the load 2.22 and the constant current source may be active elements such as transistors or resistors without compromising the effect.

1. Effects of the Invention] As described above, the amplifier circuit according to the present invention eliminates the need for an input coupling content 1 and a negative feedback bypass capacitor, and can be configured to allow direct connection. ILi Fj
It has a stable start-up effect at the time of injection.

[Brief explanation of drawings]

Ru. In the figure, ] is the input terminal, 2 is the negative feedback terminal, 3 is the output terminal,
4 is the li source terminal, R3-R4 is the resistor, z, +22 is the i load, 0+~(c is the transistor, 6 is the signal source, 7 is the negative feedback network, 8~1o is the constant current source, A is the subsequent stage Showing the amplifier. J118 Nobu Kuzumachi - No. 11' (+ No. 2 Figure 2 Procedural Amendment (Voluntary) Mr. Commissioner of the Japan Patent Office 1, Indication of the Case Patent Application No. 1982 202528 2
, Title of the invention 1 Four-width circuit 3, Representative Hitoshi Katayama of the person making the amendment Section 4, Agent 5, 7 + lj Positive Subject Specification Claims and Detailed Explanation of the Invention Column 6
Contents of extraction (1) The scope of the JF request in the detailed specification is stopped as shown in the attached sheet. (2) Item i"1 is corrected as follows. 2. Claims (1) The collector is grounded, and the emitter is connected to the power supply via the first diode and the inner column circuit of the first constant current source.
&a, and the input signals f and lj are added to the base of the first PNP transistor, and the second constant current source supplying the same current as the first constant current source and the second diode are connected in series. a second P connected to the circuit or emitter, having a collector grounded and a base grounded via the first resistor;
An eighth NPN transistor, whose base is connected to the connection point between the first diode and the first constant current source, and whose collector is connected to the gap through the first load. 1. The second tie node is connected to the contact point of the second constant current source, the collector is connected to the power supply via the second load, and the emitter is connected to the eighth transistor. A fourth npn transistor is connected to the emitter of the transistor Ha, and an eighth constant 1 is connected between the mj footer connection point of the transistor of 2.4 and ground.
a current, and a next-stage amplifier that amplifies the collector outputs of the eighth and fourth transistors, applying one current feedback from the output of the next-stage amplifier to the base of the fourth transistor through a second resistor, An amplifier circuit further comprising a negative feedback circuit network that applies AC negative feedback to the base of the second transistor. (2) A patent characterized in that it is an inverting amplifier that increases the collector output of the QIM kbl or 8F83 transistor in the next stage by l'lf. (3) In the next stage, the Amplifying non-inverting increase 1+. 1. The amplifier circuit according to item 1 of the patent scope, characterized in that it is a + amplifier.

Claims (3)

[Claims] (1) A first PNP l whose collector is grounded, whose emitter is connected to a power supply through a series circuit of an i-th diode and a first constant current source, and whose base is applied with an input signal.
- A series circuit of a transistor, a second constant current source that supplies the same current as the first constant current source, and a second diode is connected to the emitter, the collector is grounded, and the base is connected to the second diode. a second PNP grounded through a resistor of
Ranjista. an eighth NPN transistor whose base is connected to the ground point of the first diode and the first constant current source, and whose collector is connected to the power supply via the first load; a fourth npnl-transistor connected to the connection point of the second constant current source, whose collector is connected to the power supply via the second load, and whose emitter is connected to the emitter of the eighth transistor; 8th
, an eighth constant current source connected to the connection point of the emitter of the fourth transistor and the ground plane, and a next stage amplifier that amplifies the collector outputs of the eighth and fourth transistors, from the output of the next stage amplifier. An amplifier circuit having a negative feedback circuit network that applies DC feedback to the base of the fourth transistor by means of a second resistor and further applies AC negative feedback to the base of the second transistor. (2) A patent characterized in that the next stage amplifier is an inverting amplifier that amplifies the collector output of the eighth transistor. (3) The amplifier circuit according to claim 1, wherein the next stage amplifier is a non-inverting amplifier that amplifies the collector output of the fourth transistor.