Oscillators – Solid state active element oscillator – Transistors
Patent
1985-06-28
1986-11-04
LaRoche, Eugene R.
Oscillators
Solid state active element oscillator
Transistors
331145, 331176, 358148, H03K 3281
Patent
active
046212400
ABSTRACT:
In the horizontal drive of a raster scanned video display, a free running astable multivibrator responsive to a synchronization input signal provides a horizontal output signal to horizontal deflection circuitry for synchronizing the video display's raster scan with the video information presented thereon. The astable multivibrator includes a pair of coupled transistors which are alternately rendered conductive in accordance with the time constant of a respective RC network associated with each transistor. To compensate for the temperature-dependent operation of the transistor pair which causes the multivibrator's operating frequency to increase with increasing temperature, a pair of back-to-back coupled diodes are connected to provide the synchronization input signal to one RC network so as to increase the charge on a capacitor within the network, the time constant of which is similarly increased. The temperature-dependent change in voltage across the diodes compensates for the change in V.sub.BE of the transistor with temperature to maintain the time before transistor turn-on constant. A second pair of similarly coupled diodes may be connected to the second RC network to provide temperature compensation for the second transistor.
REFERENCES:
patent: 3341788 (1967-09-01), Nishioka
patent: 4253117 (1981-02-01), Kadlec
Alvord Robert J.
Amberg Robert
Fegan Michael T.
Kadlec Joseph
LaRoche Eugene R.
Mis D. C.
Zenith Electronics Corporation
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