JPH0221781Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to electronic volumes.

FIG. 1 shows an electronic volume whose signals are controlled by a conventional electronic circuit.

The music signal coming in from input terminal 1 is connected to resistor R.
0, R2, R4, and R6, and is taken out to the output terminal 4 through the amplifier 2.

The up-down counter 5 is configured so that when the switch 7 is closed, the pulse from the pulse generator 6 is counted as an up-down counter, and when the switch 8 is closed, the up-down counter 5 is counted as a down counter. has been done.
Up/down counter output Q1, Q2,
Transistors 11, 12, 1 by Q3 and Q4
3 and 14 are subject to ON/OFF control. Now, for example, if transistors 11 and 13 are turned on and transistors 12 and 14 are turned off by the output of up-down counter 5, the music signal at terminal 1 will be R1/(R1+R0) and R5/(R2+R4+R5). The signal is attenuated and taken out to the output terminal 4. However, the music signal controlled by the electronic volume configured in this way is controlled only in a stepwise manner, making it difficult to make delicate adjustments, and since switching elements are used, there is a risk that noise may be mixed into the signal system. It was hot.

The present invention provides an electronic volume that does not use the above-mentioned complicated circuits, can be controlled smoothly without steps, and is less likely to be contaminated by noise.

The voltage that is the control voltage of the VCA is used as the charging voltage of the capacitor, and it is equipped with a constant current circuit using a PNP transistor for charging and a constant current circuit using an NPN transistor for discharging, and any of the above constant current circuits The charging voltage of the capacitor is controlled by operating the capacitor, and the VCA is controlled by the voltage.

An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram of a circuit showing an embodiment of the present invention, in which a signal is supplied from input terminal 1 to VCA 22,
The signal controlled by the VCA 22 is output from the output terminal 4.

The control terminal 23 of the VCA is controlled by the output of a buffer amplifier 24 with high input impedance.

A capacitor 26 is connected to an input terminal 25 of the buffer amplifier 24, and the buffer amplifier is controlled by the voltage of the capacitor 26. The switch 27 is a switch for discharging the charging voltage of the capacitor 26 with a constant current, and the switch 28 is a switch for charging the capacitor 26 with a constant current.

Now, when the switch 28 is closed, the base current I _B1 of the transistor 32 flows through the resistor 31, and a constant base voltage V _B1 is applied by the power supply 29 and the diodes 34 and 35 connected to the base of the transistor 32. . Therefore, if the voltage between the base and emitter of the transistor 32 is V _BE1 , then the collector current I _C1 of the transistor 32 is I _C1 ≒ V _B1 − V _BE1 /R3, where the value of the resistor 38 connected to the power supply 29 and the emitter is R3. becomes.

This becomes a constant current regardless of the collector voltage of the transistor 32, and becomes a charging current for the capacitor 26.

Next, when the switch 27 is closed, the base current I _B2 of the transistor 33 flows through the resistor 30.
A constant base voltage V _B2 is applied by diodes 36 and 37 connected between the base of the transistor 33 and ground. Therefore, if the voltage between the base and emitter of the transistor 33 is V _BE2 , the collector current I _C2 of the transistor 33 will be I _C2 if the value of the resistor 39 that grounds the emitter is R4.
≒V _B1 −V _BE2 /R4. This becomes a constant current regardless of the collector voltage of the transistor 33, and becomes a discharge current of the capacitor 26.

Capacitor 26 is connected to the input terminal of buffer amplifier 24 with high input impedance. When the switches 27 and 28 are open, the transistors 32 and 33 are non-conductive and the charged control characteristics have the characteristics shown in FIG. 3, so the output voltage of the buffer amplifier 24 becomes the control voltage of the VCA. to attenuate the signal coming in from input terminal 1. Therefore, the magnitude of the signal can be smoothly controlled by the switches 27 and 28. In addition, in the above circuit configuration, the resistor 38,
When 39 is replaced with two interlocking volumes, the speed of change of the VCA control voltage can be freely selected depending on the time constant with the capacitor 26. The same holds true even if the value of the capacitor 26 is changed.

As described above, according to the present invention, an electronic volume that can perform smooth controlled attenuation and that does not include fluctuating noise or the like in the signal can be realized with a simple circuit configuration.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional electronic volume, Figure 2 is a circuit diagram of a conventional electronic volume.
The figure is a circuit diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing an example of signal attenuation versus control voltage characteristics of the VCA used in FIG. 2. 1 is the input terminal, 22 is the VCA, 4 is the output terminal,
24 is a buffer amplifier, 26 is a capacitor, 2
7, 28 are switches, 29 is a power supply, 30, 31,
38 and 39 are resistors, 32 and 33 are transistors,
34, 35, 36, and 37 are diodes.

Claims (1)

[Claims for Utility Model Registration] (1) A charging/discharging capacitor, a first transistor that conducts a base bias with a first switch and charges the capacitor with a constant current, and a second switch. The first transistor has a different polarity from the first transistor which sets the base bias to a conductive state and causes a constant current to flow and discharge from the capacitor.
a second transistor connected in series to the transistor; a hold circuit that holds the voltage charged in the capacitor; and a signal attenuated or amplified by the output of the hold circuit.
1. An electronic volume device comprising a VCA circuit and controlling the VCA circuit by turning on or off the first and second switches. (2) A variable resistor is connected in series to the emitter of each of the first and second transistors, and the emitter resistance value of the bias circuit is changed to control the amount of current and change the charging and discharging speed of the capacitor.
The electronic volume device according to claim (1) of the utility model registration, characterized in that the speed at which the VCA circuit is controlled is changed.