Posted on Feb 10, 2013

This circuit shows a simple way to add text information to a composite-video signal that might be floating at some indeterminate de level. The text generator and composite-video source must have the same sync signal. The video-input and -output signals share the same terminal. C3 couples the video signal to the output of a rectifier circuit that is based on a subvideo-speed op amp. A faster op amp would clamp on individual sync pulses rather than on the video waveform`s average value, as is desired.

Click here to download the full size of the above Circuit.

Rll serves as a pulldown resistor and feedback resistor RlO ensures that TP6 remains at ground level. Emitter follower Ql buffers the text signal, and R5 serves as a gain control. A simple clamp circuit, Q2, is sufficient for regulating amplitude, because the text signal contains no gray-scale levels. Q3 couples the text signal into the op-amp clamp circuit.

Leave Comment

characters left:

New Circuits



Popular Circuits

RF transmitter uses AMI encoding
Adjustable Regulator
Microcomputer circuit
Single Capacitor Powers Audio Mixer
Audio level meter using LM3915
Electronic projects related to computers
Simple 10W audio amplifier
gps tracker project gps module jp module lcd dispaly
Symmetrical power supply circuit electronic project
Extended common mode range of the instrumentation amplifier (INA101) circuit
Fast response time of the control transistor circuit b