JPS5840845B2 - electronic circuit - Google Patents

Description

[Detailed Description of the Invention] This invention allows human power transmission characteristics to be easily determined, and
This invention relates to an electronic circuit that obtains a direct current proportional to its output signal level.

Conventionally, to indicate the signal level, an independent amplifier is used to obtain the signal output, which is then taken out as an alternating current signal.Generally, germanium diodes with a small rise voltage (thus half-wave rectification, DC level, and full-wave rectification are used) In this case, a configuration is used in which the signal phase is inverted and the second half wave is rectified and added.

However, the above diodes and capacitors are essential,
It is not suitable for integration, and also has drawbacks such as the nonlinearity of the diode itself (due to low signal level), poor linearity with the output DC level, large temperature dependence, and unfavorable frequency characteristics. there were.

This invention attempts to eliminate these drawbacks.
An embodiment of the present invention will be described below with reference to FIG.

That is, in FIG. 1, 2 is a voltage amplifier, 1 is its input terminal, and 5 is its output terminal.

A complementary circuit 3 constitutes a driver circuit in the output stage of the amplifier 2, and is composed of an NPN transistor QN and a PNP transistor QP.

Note that this complementary circuit can be constructed of bipolar transistors and N-channel and P-channel field effect transistors.

A current mirror circuit 4 is connected to the collector of the transistor QN, and its output terminal is connected to the collector of the other transistor QP of the complementary circuit 3.

6 is a second output terminal formed at this connection point.

If the second output terminal 6 is grounded, the output terminal 5 becomes a normal amplifier output terminal that swings fully, with only the loss due to the saturation voltage valve of the mirror circuit 4.

In the meter drive circuit shown in Figure 2, 7 is a load connected to output terminal 5, 9 is a negative feedback circuit connected between input terminal 1 and output terminal 5 of amplifier 20, and 8 is a meter connected to output terminal 6. be.

As the amplifier 2, one having a large gain A is used.

Therefore, the apparent gain from the input terminal 1 to the output terminal 51 is determined only by the characteristics of the feedback circuit 9, that is, the feedback rate β, and a signal current proportional to the output voltage determined by the characteristics flows through the load 7. .

This current flows through transistor QN during the positive half cycle of the input signal and through transistor QP during the negative half cycle.

On the other hand, the current flowing through the transistor QN in the positive half cycle flows into the meter from the terminal 6 by the mirror circuit 4, and the current in the transistor QP flows into the meter from the terminal 6 in the other half cycle.

That is, the current flowing into the meter 8 becomes a full-wave rectified direct current in which the current for each positive and negative half cycle of the human input signal is aligned in one direction.

Note that since the terminal 6 is the collector output of the transistor QP button and the mirror circuit 4, its output impedance is high, and current can flow through the terminal 6 regardless of the impedance of the meter 8 connected to it.

The meter drive circuit built into the actual integrated circuit shown in Fig. 3 (in this case, Q1 to Q12 are transistors,
0 is a Darlington circuit that constitutes the input stage of the amplifier, which reduces the base current to suppress the DC feedback current from the output terminal 5, and reduces the leakage current that flows to the second output terminal 6 when there is no input signal. We are trying to reduce the number of people.

Also, the transistor Q7 corresponding to the transistor QN in FIG. 1 and FIG. 2, and the transistor Q8j, ;- and Q corresponding to the transistor QPG in FIG.
Although the complementary circuit No. 9 similarly aims to reduce leakage current as a class C operation, the distortion caused by the class C operation can be improved by increasing the open loop gain.

Rs. R1-R7, RA, RB, and Rf are resistors, among which Rf is a DC feedback resistor, and assuming the amplifier is linear, Rf/R
Determine the gain of 8.

C1 and Co are capacitors, in which capacitor C
ob and load 7 form an alternating current load.

11 is an AC feedback circuit when performing logarithmic compression amplification;
This consists of resistor RA and diode D1. It is formed by D2.

And the output of the amplifier■. is input i is multiplied by Rf/Rs,
Alternatively, it appears as logarithmically compressed amplification, and therefore ■.

A DC current IM in the form of a full-wave rectified current determined by /RL flows into the meter 8 from the terminal 6.

Moreover, among the above-mentioned resistors, RB is provided in parallel with the meter 8,
The sensitivity of the meter 8 is adjusted by branching the direct current ■゛M in an inverse ratio to the impedance of the meter 8.

This sensitivity adjustment can also be remotely achieved by making the load RL variable or by making the closed rape gain, that is, Rst or Rf variable.

Here, the voltage across the load 7 connected to the output terminal 5 is expressed as follows.

=VOsinωt, then the current io flowing through the load 7 is given by the load resistance RL, and since io is the sum of the emitter currents of the transistors Q7, QB, and Q9, the current io flowing through the load 7 is the sum of the emitter currents of transistors Q7, QB, and Q9.
.

If the leakage current at cut-off of Q9 is ignored, the collector current of transistor Q7 becomes lN1.Transistor Q8. Q
The collector current ip of 9 is here (αN and αP are transistors Q7 and Q8.

The current amplification factor of Q9 and η are the transmission ratios of the mirrors of transistors Q11 to Q12.

The collector current iN, j-P is a current flowing out from the output terminal 6, and this current can also be expressed as follows.

Current IM from output terminal 6 is collector current iN.

Since it is the sum of the half-wave rectified values of iP, the DC term is ideally (
Here, αN=αp−α.

If η-1 DC current output is obtained.

As mentioned above, according to the present invention, the number of parts is small, linearity, temperature dependence, frequency characteristics, etc. are much better than the conventional technology with the minimum number of necessary input terminals, and the meter It also becomes easier to drive.

In particular, the impedance of the meter used in this case has no small effect on the indicated value G, and several methods can be selected for its sensitivity adjustment. It is also easy to consider a specific relationship between

When incorporated into an integrated circuit, the above effects become even more remarkable.

Of course, when used as a normal amplifier, it also has the advantage of having a high degree of functional integration.

[Brief Description of the Drawings] Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram in which the circuit of Fig. 1 is applied to a meter drive circuit, and Fig. 3 is a circuit diagram showing an embodiment of the present invention.
The figure is a circuit diagram showing a state in which the meter-1 drive circuit is incorporated into an actual integrated circuit.
2...Amplifier, 3...Complementary circuit, 4...Mirror circuit, 5...Output terminal, 6...Second output Terminal, 7...
・Load, 8...Meter 9...Negative feedback circuit.

Claims (1)

[Claims] A complementary circuit is provided using transistors at the output stage of an amplifier having one pair of input/output terminals, their common emitters or common sources are used as output terminals, a current mirror circuit is connected to the collector or drain of one of the transistors, and this mirror circuit is connected to the collector or drain of one of the transistors. An electronic circuit in which the connection point between the output end of the circuit and the other collector or drain is the other output terminal.