JPH09171602A - Recording / playback circuit - Google Patents

Abstract

Kind Code: A1 Abstract: The present invention provides a recording / reproducing circuit of an electronic still camera, which has a simple circuit configuration but has good signal quality at the time of recording and reproducing. According to the present invention, switching of extra switches and the like is eliminated during recording and reproduction, a recording circuit and a reproducing circuit are simultaneously connected to a magnetic head, and power is supplied to a recording current amplification transistor through a diode. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit structure of a recording / reproducing amplifier of an electronic still camera, and more particularly to a recording / reproducing circuit and a method of supplying power to a recording current amplifying transistor.

[0002]

2. Description of the Related Art Conventionally, with respect to the structure of a recording / reproducing circuit of an electronic still camera, the structures shown in FIGS. 2 and 3 have been proposed and put into practical use. In the circuit of FIG. 2, the power supply to the circuit is switched by a switch in the recording mode and the reproducing mode, and at the time of recording, the analog switch SW4 is turned on to supply power to the recording current amplification generation transistor Q1. Is being supplied. Further, in the circuit of FIG. 3, instead of switching the power source, the three analog switches SW1 to SW3 are turned on and off to switch between the recording circuit and the reproducing circuit connected to the head at the time of recording and reproducing. ing. That is, SW1 and SW3 are turned on during recording,
Turn off SW2, and vice versa during playback, SW1 and S
W3 is off and SW2 is on.

[0003]

However, in the conventional circuit system shown in FIG. 2, a part of the reproduced signal read by the head is reproduced by the coupling capacitor C1 during reproduction, though it is good during recording. It reaches the transistor Q2 through the damping resistor R1, and at this time, since the bias voltage is not applied to Q2, it is transmitted to the power supply circuit and other loads as it is, so that the C / N is deteriorated and the secondary distortion is increased. I will let you. Alternatively, since a part of the signal reaches the PNP transistor Q2, then it goes from the collector of Q2 to the power supply system through the base and then to the ground through the circuit and the power supply impedance, so that part of the reproduction signal contributes to the reproduction. No, it becomes a loss.

Further, the circuit system of FIG. 3 requires three analog switches, and a signal loss occurs due to the resistance of the analog switches. That is, in the recording mode, the loss of the write signal occurs due to the resistance of SW3, and in the reproduction mode, the loss of the read signal of the magnetic head occurs due to the voltage drop of the resistance of SW2.

[0005]

In order to solve these problems of the prior art and to provide a new circuit configuration and method, the present invention eliminates the loss of the reproduction signal due to the transistor Q2 of FIG. Q2 is replaced with a diode, and a simple circuit in which a recording circuit, a magnetic head, and a reproducing circuit are still connected without using an analog switch as in the circuit of FIG.

That is, the present invention is a recording / reproducing circuit for an electronic still camera having a recording amplifier for amplifying a recording current sent to a magnetic head for both recording and reproduction, and a reproducing amplifier for amplifying a reproduction signal read from the magnetic head. And
One end of the magnetic head is connected to one of the power supply lines, the other end is connected to the reproduction amplifier and the recording amplifier through the respective capacitors, and during the reproducing operation, the power supply to the amplification circuit including the recording amplifier is stopped. In addition, the recording and reproducing circuit is configured so that power is supplied to the current amplification transistor at the final stage of the recording amplifier through the diode.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of the configuration of an embodiment of the present invention. One end of the recording / reproducing magnetic head H1 is grounded, and the other end is connected to the collector of the recording current amplifying transistor Q1 through the capacitor C1 and is connected to the input end of the reproducing amplifier A2 through the capacitor C2. An inductor L1 and a damping resistor R1 are connected in parallel as a collector load of the transistor Q1 and are connected to a power source through a diode D1. The power supply VCC1 for the recording circuit and the power supply VCC2 for the reproducing circuit are connected by switching between the recording mode and the reproducing mode by the switch SW5 in order to save the battery power. If a voltage is applied to the recording circuit power supply Vcc1 in the reproduction mode, the reproduction amplifier may cause unnecessary transmission depending on the values of L1 and R1 and the value of the DC bias of Q1. Therefore, it is better to separate VCC1 and VCC2. That is, the power supply to the recording circuit and the reproducing circuit is divided. Next, the operation of the circuit configuration shown in FIG. 1 will be described. First, the operation of the recording mode will be described. FM
The modulated recording signal SIG1 passes through a recording gate (not shown), and then is input to the transistor Q1 for current amplification via the recording amplifier A1. Power to Q1 is supplied through a parallel circuit of a diode D1 and an inductance L1 and a damping resistor R1. Since the DC resistance of L1 is so small that it can be ignored, the collector DC potential of Q1 is close to the potential of Vcc1 and the amplitude of the voltage signal amplified by Q1 can be increased. The recording signal generated in the collector of Q1 is supplied to the magnetic head H1 for both recording and reproduction through the capacitor C1. A part of the recording signal given to the magnetic head is transmitted to the reproducing amplifier A2 through the capacitor C2, and the input impedance of the reproducing amplifier A2 is 2 to 5 K ohms, whereas the input impedance of the magnetic head is Since it is 50 to 100 ohms, most of the recording signal is supplied to the magnetic head H1.

Next, the operation in the reproduction mode will be described. The reproduction signal read from the magnetic head H1 is supplied to the reproduction amplifier A2 through the capacitor C2 and reproduced through a reproduction circuit (not shown). At the same time, it is also supplied to the collector of the transistor Q1 through C1. Q1 is NP
In N-transistor, no current flows from the collector to the base. At this time, Vcc1 is not applied. The signal supplied to the collector of Q1 passes through R1 and the diode D1
It reaches the cathode of, but does not reach beyond.

[0009]

As described above, according to the structure and method of the present invention, the circuit structure is simple, there is no signal loss, and the signal quality is good. Furthermore, the operation is stable,
This is advantageous in manufacturing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a conventional circuit example.

FIG. 3 is a schematic diagram showing another conventional circuit example.

[Explanation of symbols]

 SIG1 recording signal SIG2 reproduction amplification signal A1 recording amplifier A2 reproduction amplifier H1 recording / reproduction magnetic head Q1 recording current amplification transistor Q2 PNP transistor D1 diode R1 damping resistor L1 inductance VCC1 recording circuit power supply VCC2 reproducing circuit power supply C1, C2 capacitor SW1 ~ SW5 analog switch

Claims (1)

[Claims] 1. A recording / reproducing circuit for an electronic still camera, comprising: a recording amplifier for amplifying a recording current sent to a recording / reproducing magnetic head; and a reproducing amplifier for amplifying a reproduction signal read from the magnetic head. One end of the magnetic head is connected to one of the power supply lines, and the other end is connected to the reproduction amplifier and the recording amplifier through respective capacitors, and during reproduction operation, power is supplied to an amplification circuit including the recording amplifier. A recording / reproducing circuit, characterized in that it is configured to be stopped, and power is supplied to a current amplification transistor at a final stage of the recording amplifier through a diode.