Sawtooth generator circuit

Posted on Feb 7, 2014

To get the best from an NBTV signal it is important to use the full dynamic range of the signal with no crushing at black level or peak white. To check the linearity of a video path it is usual to use either a staircase or sawtooth test signal. The circuit described is a free standing NBTV sawtooth generator conforming to the standard of 1volt output level and complete with 31 line sync pulses.

Sawtooth generator circuit
Click here to download the full size of the above Circuit.

The 7555 timer and LM317 regulator form a linear sawtooth generator. Two timing capacitors are employed, one setting the active line time which may be trimmed by the pot, the second sets the line sync duration. The circuit is un-usual in that the LM317 performs two roles. It acts as constant current genera-tor to linearly charge the 0. 22 mF capacitor, and also provides a very low output impedance. The 4020 counter is used as a divide-by-32 fed from line pulses. The grounded base transistor differentiates the falling edge from Q5 of the 4020 and gates out one sync pulse in 32, the output from the gate being non-inverting. The remaining 31 sync pulses are mixed with an attenuated sawtooth to form a standard 70%-30% 1 V NBTV signal and delivered at a nominal 470 © impedance.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Bridging Adapter For Power Amplifiers
    Symmetrical power supply 3-20V
    DC motor speed control
    0 to 360 phase shifter
    Backup Beeper
    CNC Controller Motion Schematics
    fm radio receiver using tda7000
    Clap Switch Circuit Project
    Super Sequencer?® With Margining Control And Auxiliary ADC Inputs
    RF Mixer Circuit
    Linux FRS Radio Control
    Thermocouple cold junction compensator AD596 597 a circuit diagram of Temperature Monitor