Precision CMOS oscillator circuit
AssigneeNational Semiconductor Corporation
InventorsMansour Izadinia, Tamas Szepesi
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Abstract
A CMOS relaxation oscillator is disclosed employing a pair of capacitors and individual charging means. A noninverting amplifier comprising two cascaded inverters is provided with a transmission gate input circuit that alternately switches the amplifier input between the two capacitors. A pair of switches coupled respectively across the capacitors alternately discharge them. The resulting oscillator has a frequency determined by the capacitor charging periods. Accordingly, the frequency and duty cycle can be predetermined as desired. The circuit can also be made either power supply tunable or power supply independent.
Claims7
An oscillator circuit operating from first and second power supply terminals connectable to a source of operating potential, said circuit comprising:
- first and second capacitors, each having a first terminal connected to one of said supply terminals and having a second terminal coupled in series through current conducting means to the opposite of said supply terminals;
- first and second switching means comprising transistors having their controlled conduction electrodes connected across said first and second capacitors respectively thereby creating two parallel connected capacitor and switching transistor combinations whereby said switching transistors can be turned on by their control electrodes to discharge the parallel connected capacitor;
- and
- means for alternately turning said switching means on thereby discharging said capacitors alternately whereby said capacitors charge alternately as a result of said current conducting means and said charge establish a timing period that determines the frequency of oscillation of said circuit.
Dependencies are inferred from the claim text.