JP2933443B2 - Positive and negative waveform separation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive / negative waveform separating circuit, and more particularly to a positive / negative waveform separating circuit used in a detecting circuit which needs to extract a positive waveform and a negative waveform faithfully to an input signal.

[0002]

2. Description of the Related Art A conventional positive / negative waveform separating circuit, as shown in FIG. 3, inputs an input signal to an inverting input of an amplifier 5 having an inverting / non-inverting input from an input terminal 1 via a resistor 13, and The output is connected to the bases of an NPN transistor 6 and a PNP transistor 7, and this NPN transistor 6
And the respective emitters of the PNP transistor 7 are connected to the inverting input of the amplifier 5. The non-inverting input of the amplifier 5 is
Connected to a bias power supply 16 via a resistor 15. The collectors of the NPN transistor 6 and the PNP transistor 7 are connected to the inputs of the first and second current mirror circuits 8 and 9, respectively.
Connected to the input of the third current mirror circuit 10, the first current mirror circuit 8 and the third current mirror circuit 10
Output terminals 2 and 3.

In the above configuration, as shown in FIG.
The input signal is converted into a current signal by the resistor 13, and when the signal has a negative waveform, the NPN transistor 6 is turned on.
Then, a current signal flows into the input terminal 1 from the emitter via the resistor 13.

When the waveform is positive, the PNP transistor 7
Is turned on, and flows into the emitter of the PNP transistor 7 from the input terminal 1 via the resistor 13.

When the NPN transistor 6 is turned on, a current signal having a negative waveform of the input signal is output (flows) from the collector to the output terminal 3 via the first current mirror circuit 8.
Is done.

When the PNP transistor 7 is turned on,
Second and third current mirror circuits 9, 10 from the collector
, A current signal having a positive waveform of the input signal is output (flows out) to the output terminal 2. Third current mirror circuit 1
Numeral 0 is a circuit added to make the current signal output from the output terminal 2 flow out.

[0007]

In such a conventional positive / negative waveform separating circuit, the current mirror circuit is formed because the circuit configuration is output via the first, second, and third current mirror circuits. NPN (also PNP) transistor 6,
7, the hFE vs. Ic characteristic, the hoe value, and the like, when the signal input by the current mirror circuit is output, various problems such as distortion and output offset occur, and faithful positive / negative waveform separation is performed. Was not done.

SUMMARY OF THE INVENTION An object of the present invention is to provide a positive / negative waveform separating circuit which solves the above-mentioned problem and faithfully separates positive and negative waveforms.

[0009]

According to the present invention, there is provided a positive / negative waveform separating circuit for inputting an input signal to a non-inverting input thereof through a first resistor.
A first amplifier for receiving a reference voltage at its inverting input;
The output of the first amplifier is inverted via a second resistor.
A second amplifier receiving the reference voltage at its non-inverting input
And when the input signal is a signal larger than the reference voltage.
A first current mirror circuit responsively responsive;
Responds when the force signal is smaller than the reference voltage.
A second current mirror circuit, and the second amplifier
The first current mirror receives the output of
An NPN transistor for generating an input current of the circuit;
The output of the second amplifier is received at its base and the NPN
Connect the emitter of the transistor to its emitter and
Connecting a connection point to the inverting input of the second amplifier;
PNP generator that generates the input current of the current mirror circuit
An NPN transistor and the NPN transistor.
The NP caused by the conditions at the time of manufacturing the PNP transistor
Characteristics of the N transistor and the characteristics of the PNP transistor
In order to suppress each variation in the characteristics, the first calendar
The output of the trimmer circuit and the second current mirror circuit
The outputs of the circuit are connected to each other, and this connection point is connected to a third resistor.
To the non-inverting input of the first amplifier via
Configuration.

[0010]

[0011]

FIG. 1 is a block diagram showing a positive / negative waveform separating circuit according to one embodiment of the present invention.

In FIG. 1, a positive / negative waveform separating circuit according to one embodiment of the present invention inputs an input signal from an input terminal 1 to a non-inverting (+) input of an amplifier 4 via a resistor 11, and The output is connected to the inverting input (−) of the amplifier 5 via the resistor 13, the output of the amplifier 5 is connected to each base of the NPN transistor 6 and the PNP transistor 7, and each of the NPN transistor 6 and the PNP transistor 7 is connected. The emitter is connected to the inverting input of the amplifier 5, the collectors of the NPN transistor 6 and the PNP transistor 7 are connected to the respective inputs of the current mirror circuits 8, 9, and the first outputs of the current mirror circuits 8, 9 are connected. Then, the connection point 20 is connected to the non-inverting input of the amplifier 4 (or via the resistor 12), and the bias source 16 is connected to the inverting input of the amplifier 4 and the non-inverting input of the amplifier 5. Connected through a resistor 14 and 15 Risorezore.

From the second output of the current mirror circuit 9,
The signal is output to the output terminal 2 via the current mirror circuit 10. The second output of the current mirror circuit 8 is the output terminal 3
Output more.

As described above, the positive / negative waveform separating circuit of the present embodiment includes an amplifier for negatively feeding back a signal obtained by combining the positive and negative waveforms separated positive and negative waveforms to the input of the conventional positive / negative waveform separating circuit. Have.

Next, the operation of this configuration will be described. Input signal input from input terminal 1 (waveform at input terminal 1 in FIG. 4)
Has a positive waveform (oblique line), flows into the first output of the current mirror circuit 9 via the resistors 11 and 12 as a positive current signal (waveform at the node 20). This waveform signal is referred to as (A). At this time, the output of the amplifier 4 swings more positively (in phase with the input signal) than the potential of the bias source 16 and the resistance 13
, Flows into the emitter of the PNP transistor 7 as a positive current signal (B), flows from the collector via the current mirror circuit 9, and from the first output via the resistors 11 and 12, and has a positive waveform. (A) is subtracted. When the input signal has a negative waveform, it flows out as a negative current signal (C) from the first output of the current mirror circuit 8 via the resistors 11 and 12. At that time, the output of the amplifier 4 swings more negatively than the potential of the bias source 16 and flows out as a negative current signal (D) from the emitter of the NPN transistor 6 via the resistor 13.
The current flows from the collector via the current mirror circuit 8 and the resistors 11 and 12 from the first output similarly to the positive current signal. The current signal (C) having a negative waveform flows out. These two amplifiers constitute two negative feedback circuits. A current signal having a positive waveform (the waveform at the output terminal 2 in FIG. 4) flows out of the second output of the current mirror circuit 9 to the output terminal 2 via the current mirror circuit 10. Further, a current signal having a negative waveform (a waveform at the output terminal 3: (C)) flows out from the second output of the current mirror circuit 8 to the output terminal 3. The current mirror circuits 8, 9, 10 have the same input / output ratio,
When 3 has the same value, the positive current signals (A) and (B) have the same value, and the negative current signals (C) and (D) also have the same value.

The resistor 12 has the same value as the load connected to the output terminals 2 and 3 when the effect is improved by the hoe value (Early effect) of the NPN (or PNP) transistors included in the current mirror circuits 8 and 9. .

The resistors 14 and 15 are inserted to eliminate the input offset of the amplifiers 4 and 5.

FIG. 2 is a block diagram of another embodiment of the present invention. In FIG. 2, this embodiment is an embodiment in which the current negative feedback configured by the amplifier 4 of FIG. 1 is changed to a voltage negative feedback configuration.

That is, the input terminal 1 is connected to the inverting input of the amplifier 4 or the inverting input via the resistor 14 in order to improve the input offset.
And the resistance (load resistance) from the connection point 21
12 is connected. The other end of the resistor 12 is connected to a bias source 16. Other components are the same as those in FIG.

The waveform at the connection point 21 is as shown in the figure.
The operation of the present embodiment is the same as that of the above-described embodiment, and will not be described.

[0021]

As described above, according to the present invention, the signals after the separation of the positive and negative waveforms are synthesized and the current or the voltage is negatively fed back to the amplifier, so that the signals are generated in the first and second current mirror circuits. The distortion and output offset are compressed to 1 / gain of the amplifier, so that positive and negative waveforms faithful to the input signal can be obtained from the two output terminals.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a positive / negative waveform separation circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a positive / negative waveform separation circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventionally used positive / negative waveform separation circuit.

FIG. 4 is a waveform chart showing operation waveforms of respective units in FIGS. 1 to 3;

[Explanation of symbols]

 Reference Signs List 1 input terminal 2, 3 output terminal 4, 5 amplifier 6 NPN transistor 7 PNP transistor 8, 9, 10 current mirror circuit 11, 12, 13, 14, 15 resistor 16 bias source

Claims (1)

(57) [Claims] An input signal is supplied to a non- inverting signal through a first resistor.
A first amplifier receiving an inverted input and receiving a reference voltage at an inverted input
And the output of the first amplifier through a second resistor.
The second receiving the reference voltage on the non-inverting input and receiving the reference voltage on the non-inverting input
And a signal whose input signal is larger than the reference voltage.
Current mirror circuit responding in response to a signal
And when the input signal is a signal smaller than the reference voltage.
A second current mirror circuit responsively responsive to said second current mirror circuit;
The first amplifier receives the output of the second amplifier at its base.
NPN Transistor that Generates the Input Current of the Transistor Mirror Circuit
And the output of the second amplifier is received at its base.
Connect the emitter of the NPN transistor to its emitter
And connects this connection point to the inverting input of the second amplifier.
And generates an input current of the second current mirror circuit.
A PNP transistor, and the NPN transistor
And manufacturing conditions of the PNP transistor
Characteristics of the NPN transistor and the PNP transistor
In order to suppress each fluctuation of transistor characteristics,
The output of the first current mirror circuit and the second current mirror
Connected to the output of each
A third resistor is connected to the non-inverting input of the first amplifier.
A positive / negative waveform separation circuit characterized by connecting back and forth.