Automatic sweep circuit
AssigneeTrio Kabushiki Kaisha
InventorTadaaki Goto
Life of this patent
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Abstract
An input signal is converted into a dc voltage proportional to the frequency of the input signal in a frequency-voltage converter, while saw tooth waves are generated in a saw tooth wave generator triggered with the input signal. The dc voltage is applied to a variable resistance circuit where the resistance is changed corresponding to the dc voltage. The period of such saw tooth waves is controlled with the variable resistance circuit so that the saw tooth waves may follow the input signal frequency for automatically indicating at all times a desired number of waveforms on the screen of a cathode-ray tube. The variable resistance circuit may be controlled with means for free running operation of the saw tooth wave generator during the absence of the input signal.
Claims2
An automatic sweep circuit comprising:
- frequency voltage converter circuit means connected to a source to receive therefrom an input signal, to generate input pulses, and to convert said pulses to a d.c. voltage proportional to the frequency of said input signal;
- saw tooth wave generator means connected to said source for generating saw tooth waves when triggered by said input signal;
- and
- variable resistance circuit means, connected to said frequency voltage converter means and to said saw tooth wave generator means, for controlling said saw tooth wave generator means by controlling the period of said saw tooth waves such that said saw tooth waves automatically follow said frequency of said input signal, said variable resistance circuit means comprising an operational amplifier having an input connected to said frequency voltage converter circuit means to receive therefrom said d.c. voltage and an output, and a field effect transistor serially connected between the output of said saw tooth wave generator means and said input of said operational amplifier, said field effect transistor having a gate connected to said output of said operational amplifier, the gate voltage of said field effect transistor thereby being controlled by said output of said operational amplifier.
Dependencies are inferred from the claim text.