JPH11122058A - Reference voltage generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference voltage generation circuit capable of supplying two bias voltages by current output for one path and an operational amplifier and reducing the number of elements. SOLUTION: In a DC circuit 50 for performing the offset correction and bias adjustment in recording and reproducing audio signals, the audio signals from an input terminal in are voltage/current converted by a voltage/current conversion circuit part 50A and outputted to an invertible amplifier circuit part 50B. The invertible amplifier circuit part 50B is provided with an operational amplifier 80 for constituting a first invertible amplifier circuit and an operation amplifier 82 for constituting a second invertible amplifier circuit. From the output terminal out1 of the operational amplifier 80, an output voltage Vout1 by the bias voltage V1 which is optimum for a power source Vcc1 is outputted. Also, from the output terminal out2 of the operational amplifier 82, the output voltage Vout2 by the bias voltage V2 optimum for the power source Vcc2 is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reference voltage generating circuit for supplying an optimum bias according to each power supply voltage in a circuit system having a plurality of power supplies.

[0002]

2. Description of the Related Art Conventionally, when recording a video signal, for example, as an 8 mm video tape recorder, an audio signal input from a microphone or the like is subjected to a level limiting process or a noise removing process, and then FM-modulated and recorded on a tape. When the video signal is reproduced, the recorded audio signal is
2. Description of the Related Art A recording / reproducing circuit AFM (Audio Frequency Moduration) system that demodulates, reproduces, and outputs to a headphone or the like is known.

In such an audio signal recording / reproducing circuit, two types of power supplies Vcc1 and Vcc2 are provided in order to reduce power consumption, and a headphone output amplifier for outputting an audio signal is equal to Vcc1. Alternatively, the larger power supply Vcc2 is used, and for most other circuits, the smaller power supply Vcc1 is used. Therefore, in such a recording / reproducing circuit, an optimal bias voltage is applied to each of the power supplies Vcc1 and Vcc2 in a DC circuit provided in an audio signal transmission path and performing offset correction thereof.

FIG. 3 is a circuit diagram showing a configuration example of such a DC circuit. In this DC circuit, at the time of recording, an audio signal that has been subjected to level limitation and filtering is input from a microphone (not shown) to an input terminal in, performs offset correction on the audio signal, and applies a first bias voltage V1 to the input terminal in. 1 from the output terminal out1
Output to the modulation circuit. At the time of reproduction, an audio signal demodulated from an FM demodulation system is input to an input terminal in, and the audio signal is subjected to offset correction, applied with a first bias voltage V2, and output from a second output terminal out2. Output to the amplifier.

Hereinafter, the details of the DC circuit will be described. First, a high-frequency component included in an input signal is removed by a low-pass filter including a DC circuit of a resistor R11 and an external capacitor C0.
12 and an operational amplifier 110, 112, 114, 116. In the voltage-current conversion circuit, a current corresponding to the AC amplitude component of the input voltage is generated by the resistor R12, and the operational amplifier 11
0, 112 and 114 are input to the inverting input terminals. In the operational amplifier 110, a direct current is generated and fed back to the inverting input terminal, and this is supplied to two operational amplifiers 112, 1
14 inverting terminals. The operational amplifier 116
Is the component V removed by the low-pass filter described above.
10 and the inverting input terminal of the operational amplifier 110 are imaginarily short-circuited.

With such a configuration, the operational amplifier 11
From 2, 114, only the current signal corresponding to the AC amplitude component of the input voltage is output. The current output of the operational amplifier 112 is output to an operational amplifier 120 for applying a first bias voltage V1, and the current output of the operational amplifier 114 is converted to an operational amplifier 122 for applying a second bias voltage V2. 124.

The operational amplifier 120 constitutes an inverting amplifier circuit. The output terminal of the operational amplifier 112 is connected to the inverting input terminal, and the first bias voltage (V1) power supply 130 is connected to the non-inverting input terminal. ing. The output terminal of the operational amplifier 120 is connected to an inverting input terminal via a feedback resistor R20, and this output terminal is the first output terminal out1 of the above-described DC circuit. From this first output terminal out1, an output voltage Vout1 with a bias voltage V1 optimal for Vcc1 is output.

The operational amplifiers 122 and 124 form an inverting amplifier circuit. The inverting input terminal of the operational amplifier 122 is connected to the output terminal of the operational amplifier 114, and the non-inverting input terminal is connected to the second bias voltage (V2). Power supply 132 is connected. The output terminal of the operational amplifier 122 is connected to the inverting input terminal via a feedback resistor R21, and the output terminal is connected to the inverting input terminal of the operational amplifier 124 via a resistor R22.

The non-inverting input terminal of the operational amplifier 124 is connected to a second bias voltage (V2) power supply 132 via a parallel circuit of resistors R23 and R24. Further, the output terminal of the operational amplifier 124 is connected to the inverting input terminal via the feedback resistor R25, and this output terminal is the second output terminal out2 of the above-described DC circuit. From this second output terminal out2, an output voltage Vout2 with a bias voltage V2 optimal for Vcc2 is output. Here, the resistance values of the resistors R22 and R23 are equal, and the resistance R
It is assumed that the resistance value of the resistor 24 is equal to the resistance value of the resistor R25.

[0010]

However, when a bias is applied by the configuration shown in FIG. 3, in order to obtain two output voltages Vout2 and Vout1, two current output operational amplifiers 112 and 114 for two paths are provided. In addition, the operational amplifiers 120, 122, and 124 are required, resulting in a problem that the number of elements in the circuit increases and the cost increases. SUMMARY OF THE INVENTION It is an object of the present invention to provide a reference voltage generating circuit that can supply two bias voltages by a current output for one path and an operational amplifier, thereby reducing the number of elements.

[0011]

According to the present invention, there is provided a first reference voltage power supply, a second reference voltage power supply, a voltage-current conversion circuit for converting an input voltage to a current output, and A first reference voltage source connected to a non-inverting input terminal, an output terminal of the voltage-current converting circuit connected to an inverting input terminal, and an output terminal connected back to the inverting terminal;
And an output terminal of the first inverting amplifier circuit is connected to an inverting input terminal via a first resistor, and a non-inverting input terminal of the first inverting amplifier circuit is connected in series. A third reference voltage power supply via a third resistor and a fourth resistor, a connection point between the third resistor and the fourth resistor to a non-inverting input terminal, and an output terminal to an inverting terminal. A second inverting amplifier circuit connected in a feedback manner, wherein the ratio of the first resistor to the second resistor is equal to the ratio of the third resistor to the fourth resistor; The output of the amplifier circuit is a first bias voltage output, and the output of the second inverting amplifier circuit is a second bias voltage output.

In the reference voltage generating circuit of the present invention as described above, the output terminal of the first inverting amplifier is connected to the first terminal.
An output voltage corresponding to the voltage value of the reference voltage power supply is output, and an output voltage corresponding to the voltage value of the second reference voltage power supply is output to the output terminal of the second inverting amplifier circuit.
Therefore, output voltages with two different bias voltages can be obtained by the two inverting amplifier circuits, and the current output and the path of the inverting amplifier circuit are two paths in accordance with each bias voltage.
Since it is not necessary to provide one, the number of elements can be reduced, and the circuit configuration can be simplified and the cost can be reduced.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reference voltage generating circuit according to the present invention will be described below. FIG. 1 is a circuit diagram showing a configuration example of a reference voltage generation circuit according to the present invention. FIG. 2 is a block diagram showing an audio signal recording / reproducing circuit (AFM system) provided with the reference voltage generating circuit shown in FIG. 1. FIG. 2A shows a signal path during recording.
(B) shows a signal path at the time of reproduction.

First, an outline of the AFM system of the present embodiment will be described with reference to FIG. The AFM system of this example is provided in a portable 8 mm video tape recorder, and when recording a video signal, FM-modulates an audio signal input from a microphone and records it on a tape. Also,
During reproduction of a video signal, an audio signal recorded on a tape is FM-demodulated and reproduced, and output to headphones.

In FIG. 2A, at the time of recording an audio signal, an audio signal input from a microphone is subjected to level limiting processing by an unillustrated auto-level controller, noise is removed by an audio band-pass filter circuit, and then input terminal in is input to the DC circuit 50. The DC circuit 50 performs offset correction on the input audio signal with respect to variations in characteristics between elements and the like, and outputs the audio signal adjusted by the first bias voltage V1 corresponding to the power supply voltage Vcc1 from the first output terminal out1. While sending it to the FM modulation system,
The audio signal adjusted by the second bias voltage V2 corresponding to the power supply voltage Vcc2 is output to the second output terminal out.
2 to the headphone output amplifier 60.

The FM modulation system includes a matrix circuit (MATRIX) 52 for performing signal processing, a noise reduction circuit (NR) 54 for removing noise, and a modulation circuit (MOD).
The audio signal from the DC circuit 50 is FM-modulated along this path and recorded on a tape by a recording / reproducing mechanism (not shown).

In FIG. 2B, at the time of reproducing an audio signal, an FM-modulated audio signal reproduced from a tape by a recording / reproducing mechanism is demodulated by a demodulation circuit 56, and a noise reduction circuit 54 and a matrix circuit 52 are provided.
, And inputs the demodulated audio signal to the DC circuit 50. In the DC circuit 50, the input demodulated audio signal is offset-corrected and a second signal corresponding to the power supply voltage Vcc2 is corrected.
The audio signal adjusted by the bias voltage V2 of the headphone output amplifier 60 from the second output terminal out2.
To send to.

That is, in such an AFM system, two types of power supplies Vcc1,
Vcc2 is provided, and a headphone output amplifier 60 that outputs an audio signal uses a power supply Vcc2 that is equal to or greater than Vcc1, and uses a smaller power supply Vcc1 for most other circuits. The DC circuit 50 applies the optimum bias voltages V1 and V2 to the power supplies Vcc1 and Vcc2 during recording and reproduction of the audio signal as described above.

Hereinafter, the DC circuit 5 of the present embodiment will be described with reference to FIG.
0 will be described in detail. The DC circuit 50 includes a voltage-current conversion circuit unit 50A that offset-corrects a voltage signal input to the input terminal in and converts the voltage signal into a current signal, and a DC-current conversion circuit unit 50A based on the current output from the voltage-current conversion circuit unit 50A. And an inverting amplifier circuit 50B for obtaining various types of bias voltage outputs Vout1 and Vout2.
As described above, the configuration in which the input voltage is converted to the current and the bias is adjusted by the inverting amplifier circuit achieves lower power consumption than the configuration using the non-inverting amplifier circuit.

Next, the voltage-current conversion circuit section 50A includes a low-pass filter constituted by a DC circuit of a resistor R1 and an external capacitor C1, and a voltage-current filter constituted by a resistor R2 and operational amplifiers 70, 72 and 74. A current conversion circuit. The voltage signal input to the input terminal in is
The high-frequency component is removed by the low-pass filter and supplied to the voltage-current conversion circuit.

In the voltage-current conversion circuit, a current corresponding to the AC amplitude component of the input voltage is generated by the resistor R2 and input to the inverting input terminals of the operational amplifiers 70 and 72. The operational amplifier 70 generates a DC current, feeds it back to the inverting input terminal, and supplies it to the inverting terminal of the operational amplifier 72 for current output. The operational amplifier 74 includes the component V10 removed by the low-pass filter described above and the operational amplifier 70.
Of the inverting input terminal is short-circuited.

With such a configuration, the operational amplifier 72 outputs only a current signal corresponding to the AC amplitude component of the input voltage. Then, the current output of the operational amplifier 72 is supplied to the inverting amplifier circuit unit 50B. Inverting amplifier circuit 50B
Comprises: an operational amplifier 80 forming a first inverting amplifier circuit;
It has an operational amplifier 82 constituting a second inverting amplifier circuit.

First, the output terminal of the operational amplifier 72 is connected to the inverting input terminal of the operational amplifier 80. The first bias voltage (V) is applied to the non-inverting input terminal of the operational amplifier 80.
1) Power supply 90 is connected. The operational amplifier 80
Is connected to an inverting input terminal via a feedback resistor R3. The output terminal of the operational amplifier 80 is connected to the inverting input terminal of the operational amplifier 82 via the resistor R4. The first bias voltage (V1) power supply 90 and the second bias voltage (V2) power supply 92 are connected via series-connected resistors R5 and R6, and each of the resistors R5 and R6
Is connected to the non-inverting input terminal of the operational amplifier 82. The output terminal of the operational amplifier 82 is connected to an inverting input terminal via a feedback resistor R7. And
The ratio between the resistors R4 and R7 is equal to the ratio between the resistors R5 and R6, that is, R4 × R6 = R5 × R7.

With such a configuration, the output terminal of the operational amplifier 80 is connected to the first output terminal o of the DC circuit 50 described above.
ut1. From this first output terminal out1, an output voltage Vout1 with a bias voltage V1 optimal for Vcc1 is output. The output terminal of the operational amplifier 82 is connected to the second output terminal out of the DC circuit 50 described above.
It is 2. From the second output terminal out2, V
Output voltage Vou by bias voltage V2 optimal for cc2
t2 is output.

Next, the output voltages Vout1 and Vout2 in the inverting amplifier circuit section 50B having the above configuration will be described. Note that the resistance R5 = k × R4 and the resistance R6 = k
× R7, and V2 ≧ V1. The operational amplifier 82
V3 is the voltage value at the non-inverting input terminal.

First, Vout1 = V1. Next, V
3 is

## EQU1 ##

(Equation 1) Also, Vout2 = V3 + {(V3-V1) / R4} × R7 = {1+ (R7 / R4)} × V3- (R7 / R4) × V1 = {(R4 × V2 + R7 × V1) / R4} − (R7 / R4) × V1 = V2 Therefore, the optimal bias V1 for Vcc1 can be applied to the Vcc1 path, and the optimal bias V2 for Vcc2 can be applied to the Vcc2 path. The same applies to a case where each of the bias voltage power supplies 90 and 92 is changed as a variable voltage, and it is possible to follow a power supply voltage changing apparatus.

[0027]

As described above, in the reference voltage generating circuit of the present invention, based on one current output from the voltage-current conversion circuit, the first output terminal of the inverting amplifier circuit connected in two stages is used as the first output terminal. A bias voltage output and a second bias voltage output can be obtained. Therefore, there is no need to provide two paths for the current output and the inverting amplifier circuit corresponding to the two bias voltages, so that the number of elements can be reduced, and the circuit configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a reference voltage generation circuit according to the present invention.

FIG. 2 is a block diagram showing an audio signal recording / reproducing circuit provided with the reference voltage generating circuit shown in FIG. 1;
2A shows a signal path at the time of recording, and FIG. 2B shows a signal path at the time of reproduction.

FIG. 3 is a circuit diagram illustrating a configuration example of a conventional DC circuit.

[Explanation of symbols]

50A... Voltage-current conversion circuit section, 50B... Inverting amplification circuit section, 70, 72, 74, 80, 82... Operational amplifier, 90, 92.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sachie Yoshizawa 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Masaki Yoshihara 5-1 Noguchikita, Kokubu-shi, Kagoshima Sony (72) Inventor Kazue Toguchida 5-1 Noguchikita, Kokubu-shi, Kagoshima Prefecture Sony Kokubu Corporation (72) Inventor Yoshihiro Kubota 2-20-1, Yasutori, Nishi-ku, Nagoya-shi, Aichi Meitec Corporation Inside

Claims (4)

[Claims] 1. A first reference voltage power supply, a second reference voltage power supply, a voltage-current conversion circuit for converting an input voltage to a current output, and an output terminal of the voltage-current conversion circuit connected to an inverting input terminal. And a first inverting amplifier circuit in which the first reference voltage power supply is connected to a non-inverting input terminal and an output terminal is feedback-connected to an inverting terminal; and an output terminal of the first inverting amplifier circuit is a first inverting amplifier circuit. A non-inverting input terminal of the first inverting amplifier circuit is connected to the second reference voltage power supply via a third resistor and a fourth resistor connected in series, while being connected to an inverting input terminal via a resistor. And
A second inverting amplifier circuit in which a connection point between the third resistor and the fourth resistor is connected to a non-inverting input terminal, and an output terminal is feedback-connected to an inverting terminal; The ratio between the resistance and the ratio between the third resistance and the fourth resistance is equal, and the output of the first inverting amplifier is used as the first bias voltage output, and the output of the second inverting amplifier is output. A reference voltage generation circuit, wherein is a second bias voltage output. 2. The reference voltage generating circuit according to claim 1, wherein a voltage level of said second reference voltage power supply is equal to or higher than a voltage level of said first reference voltage power supply. 3. The voltage-current conversion circuit performs offset correction of an input voltage, generates a current output corresponding to an AC amplitude component of the input voltage, and outputs the current output to an inversion of the first inversion amplification circuit. 2. The reference voltage generation circuit according to claim 1, wherein the reference voltage is supplied to an input terminal. 4. The reference voltage generating circuit according to claim 1, wherein at least one of said reference voltage power supplies is a variable voltage power supply.