JPH01200708A - differential amplifier device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a differential amplifier device using a differential amplifier as an amplifying element.

2. Description of the Related Art In the fields of video and audio, a differential amplifier, not shown in FIG. 2, has been used. Non-inverting input side (-1-) of differential amplifier 1
is connected via a resistor 5 to a reference voltage vr created by dividing the power supply voltage VCC with a series circuit of resistors 2 and 3, and stabilizing the voltage across resistor 3 with a capacitor 4. An input signal S is applied to the inverting input +flj+ <-1-) via the first capacitor 6. The inverting input side (-) of the differential amplifier 1 is grounded via a resistor 7 and a second capacitor 8. A resistor 10 is interposed between the inverting input side (-) and the output side 9 of the differential amplifier 1,
The gain of differential amplifier 1 is determined by resistors 7 and 10.

Conventionally, the transistor 11 is used for charging the first capacitor 6, or the transistor 1 is used for charging the second capacitor 8.
2 or 8 St, and the charging operation is executed as follows immediately after the power is turned on.

After the power is turned on, the voltage across the capacitor 4 is the power supply voltage ■
(The voltage Vr is divided by the resistors 2 and 3, and the first and second capacitors 6
．． A charging current flows through 8. 1st. second capacitor 6,
8 is rapidly charged until the emitter potential of the transistor 11, the emitter potential of the transistor 12, or the reference voltage vr becomes one voltage lower than the reference voltage vr, or after that, the resistor 5, the first capacitor 6, and Resistor 7, 10
, and is slowly charged to the reference voltage Vr with a time constant determined by the second capacitor 8.

Problems to be Solved by the Invention In such a conventional configuration, first. second capacitor 6
．． 8, it takes time to charge from a potential one diode lower than the reference voltage Vr to the reference voltage Vr. 1st. If the capacitance value of the second capacitor 6.8 is different, additional time is required for charging, and the differential amplifier 1
There is a problem in that it takes time for the amplified output to be generated on the output side 9 of the amplifier.

The present invention provides a first input terminal connected to a non-inverting input side and an inverting input side of a differential amplifier. It is an object of the present invention to provide a differential amplifier device in which a second capacitor is rapidly charged to a reference voltage and an amplified output is rapidly generated on the output side of a differential amplifier.

Means for Solving the Problems The differential amplifier device of the present invention applies a reference tJE to one of the non-inverting input side and the inverting input side of a differential amplifier, and The configuration is such that an input signal is applied, the other input is grounded via a second capacitor, and the amplified output is taken out from the output side of the differential amplifier. a bias circuit that turns on the transistor; a switch means that connects one ends of the second capacitors to have the same potential; and a switch means that connects the base of the second transistor to the negative input side and the emitter of the first transistor, and connects the collector of the second transistor. the emitter circuit of the second transistor is connected to a higher potential than the reference voltage, the output of the Schmitt circuit is connected to the bias circuit, and one end of the Schmitt circuit is connected to the other by the switch means. 1st. The second capacitor is connected to the first capacitor. charging through the second transistor; When the one end of the second capacitor is charged to the reference voltage, the Schmitt circuit is inverted and the first end is charged to the reference voltage. The present invention is characterized in that the second transistor is turned off to turn off the switch means.

Effect According to this configuration, when charging immediately after turning on the power, the first
．． One ends of the second capacitors are connected to each other by the switch means, and in this state, the ends of the first... 2nd--5= transistors at a voltage higher than the reference voltage.
The second capacitor is charged, and when the charging reaches the reference voltage, the Schmitt circuit charges the first capacitor. The second transistor is turned off to 1, and the switch means is also turned off.

Example An embodiment of the present invention will be described below with reference to FIG.

Components having the same functions as those in FIG. 2 showing the conventional example will be described with the same reference numerals.

FIG. 1 shows a differential amplifier according to the present invention, and FIG. 2 shows a conventional example. Only the charging circuit of the second capacitor 6.8 is different. A power supply voltage VCC is applied to both ends of a bias circuit 16 consisting of a series circuit of resistors 13.14°15, and the first transistor Q is applied immediately after the power is turned on.
Turn on 1. Q5.

Q6 is a transistor constituting the switch means 17, whose collector and emitter are connected in antiparallel, one end of which is connected to the connection point of the first capacitor 6 of the resistor 5, and the other end of which is connected to the connection point of the resistor 7 and the second capacitor. It is connected to 8 connection points,
By being in the on state, the first. Second capacitor6.
It acts to connect one end of 8 to each other so that they have the same potential.

The emitter of the second transistor Q2 is connected to the power supply voltage Vcc via a resistor 18, and the first capacitor 6 is connected to the non-inverting input side (+) of the differential amplifier 1.
The base is connected to the connection point of the switch means 17 and the emitter of the first transistor Q1. The collector of the second transistor Q2 is connected to the control 9 of the switch means 17.
Said transistor Q5. as +1 terminal. Connected to the base of Qs. Q3.

Q4 is a transistor that constitutes the Schmint circuit 19,
The transistor Q3 has an emitter connected to the power supply voltage VCC via a resistor 18, a base connected to the connection point between the resistors 14 and 15 forming the bias circuit 16, and a collector connected to the resistor 2.
0 to ground. The transistor Q4 has its base and emitter connected to both ends of the resistor 20, and its collector and emitter connected to both ends of the bias circuit 1% 16 resistor 15.

Because of this configuration, the first. Second capacitor6.
8 is charged as follows. Since the bias circuit 16 does not have a capacitor, it is most stable when the power is turned on, the first transistor Q1 supplies current, the transistors Q3 and Q4 are cut off, and the second transistor Q2 and the switch means 17 transistor Q5 of
, Qs turns on. If the second transistor Q2 is on, the emitter voltages of the transistors Q5 and Q6 are equal, and the first... One ends of the second capacitor 6.8 are connected to each other. Now, set the voltage of capacitor 4 to V
c, the base potential Ve1 of the first transistor Q1
is set to a voltage of one diode or more -L below Vc. Further, the resistor 19 is selected so that the transistor Q4 is turned on when the base potentials of the second transistor Q2 and the transistor Q3 become equal, and the base potentials e3 and Vc2 of the transistor Q3 are kept at the same potential.

In this state, rapid charging is performed by the emitter current of the first transistor Q1 and the collector current of the second transistor Q2. When the base potential VB2 of the second transistor Q2 becomes the same potential as ve3, the transistors Q3 and Q4 are turned on and the first. The second transistor (h
, Q2 and transistors Q5 and Qs are turned off, and a state is maintained in which the above charging circuit has no effect on the amplifier circuit of the differential amplifier 1. Note that since the switching means 17 sets one ends of the first and second capacitors 6.8 to the same potential to perform a charging operation, the first and second capacitors 6.8 are charged. Even if the second capacitors 6.8 have different capacitance values, they can be quickly charged.

Effects of the Invention As described above, according to the present invention, when charging immediately after power is turned on, the first. The base W-lightning voltage is also high through the second transistor to the first transistor. Because the second capacitor is charged, the first capacitor is charged more quickly than before. A second capacitor can be charged. Moreover, during this charging, the switch means switches the first to the first. Since one end of the second capacitor is connected to each other, charging can be completed quickly even if the capacitance values of the first and second capacitors are different, and the output side of the differential amplifier This can be accomplished by quickly obtaining amplified output. Despite adding such a charging circuit,
1st. The second transistor and the switch means are of good quality and do not cause cut-off effects due to the Schmitt circuit when charging is completed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of a differential amplifier according to the present invention;
FIG. 2 is a block diagram of a conventional differential amplifier. DESCRIPTION OF SYMBOLS 1... Differential amplifier, 6... First capacitor, 8...
...Second capacitor, 16...Bias circuit, 17
...Switch means, 19...Schmitt circuit, Ql
...first transistor, Q2...second transistor. Agent Yoshihiro Morimoto-1 () -=

Claims (1)

[Claims] 1. Apply a reference voltage to one of the non-inverting input side and the inverting input side of the differential amplifier, apply the input signal via the first capacitor, and connect the other input to the second capacitor. The amplifier is grounded through the differential amplifier and the amplified output is taken out from the output side of the differential amplifier. a switch means that connects one ends of the capacitors to have the same potential; a base of a second transistor is connected to the one input side and the emitter of the first transistor; and a collector of the second transistor is connected to the emitter of the first transistor; a control terminal, an emitter circuit of the second transistor is connected to a potential higher than the reference voltage, and an output of the Schmitt circuit is connected to the bias circuit;
charging first and second capacitors, the ends of which are connected to each other by the switch means, via the first and second transistors;
A differential drive circuit configured to invert the Schmitt circuit to cut off the first and second transistors and turn off the switch means when the one ends of the first and second capacitors are charged to the reference voltage. Amplifier.