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video amplifiers

The amplifier will be an indispensable component of your home surveillance system with cameras and remote installation, possibly, It will be widely used in professional circles. A distinctive feature of the device is the possibility of mounting a cable break, that adds maximum device functionality. Set, certainly, It will be interesting and useful to explore the basics of electronics and receiving assembly experience and customization of devices.

1Specifications.

Supply voltage: 8... 15(nominal 12 AT).

Consumption current: 25... 40 mA.

input impedance: 75 ohm.

load resistance: 75 ohm.

Gain Au: 0... 15 dB.

frequency band (video),no less: 6 MHz.

PCB Dimensions: 60×25 mm.

Description of module operation.

The amplifier is designed for classical transistor switching circuit with common base (VT1). This is why the low-resistance input impedance of the device is determined and, actually, the nominal value of the resistor R1 (75 ohm). On the transistor VT2 assembled reference current source for VT1. The transistor forming an emitter follower VT3 (a reference current source to VT4), whereby VT1 is not shunted low impedance load, and the output impedance of the amplifier depends on the minimum and R9 (75 ohm).

details:

2Properly assembled video amplifier requires no configuration.

However, before using it is necessary to do several operations.

1.Check the installation. Attention! Especially check the correct installation of transistors, diodes and electrolytic capacitors.

2.Check connection source, the load and the supply voltage.

3.Install the engine tuning resistor R2 to the left, that corresponds to unity gain.

4.Apply power.

5.Rotating the engine tuning resistor R2, set the desired gain.

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