Abstract An amplifier comprises a power amplifying circuit including FET's and operable when supplied with a first power source and a drive circuit operable when supplied with a second power source for driving the power amplifying circuit and including a bias circuit for providing bias voltages for the FET's. Upon turning on the power switch, the first power source builds up quickly while the second power source builds up with some time delay. Switch-over circuits connect the power lines of the drive circuit to the first power source initially and to the second power source after the build-up of the latter, thereby starting the supply of the bias voltages to the FET's at the build up of the first power source to prevent an excessively large current or rush current from flowing through the FET's, thus avoiding the breakage or characteristic deterioration of the FET's.
An amplifier comprising: a first power source building up quickly upon power-on of the amplifier; a second power source building up with a time delay as compared with said first power source upon power-on of the amplifier; a power amplifying circuit connected to said first power source and including at least one FET; a drive circuit connected to said power amplifying circuit for driving the latter, and including means for providing at least one bias voltage for said at least one FET; and switch-over means connected to said drive circuit, said first power source and said second power source for supplying, to said drive circuit, power from said first power source before said second power source builds up and power from said second power source after said second power source builds up.
Claim 2
Dependent Claim
132 words
An amplifier comprising: a first power source building up quickly upon power-on of the amplifier; a second power source building up with a time delay as compared with said first power source upon power-on of the amplifier; a power amplifying circuit connected to said first power source and including at least one FET; a drive circuit connected to said power amplifying circuit for driving the latter, and including means for providing at least one bias voltage for said at least one FET; and switch-over means connected to said drive circuit, said first power source and said second power source for supplying, to said drive circuit, power from said first power source before said second power source builds up and power from said second power source after said second power source builds up.
Claim 3
Dependent Claim
14 words
An amplifier according to claim 1, wherein: said FET is of a depletion mode.
Claim 4
Dependent Claim
16 words
An amplifier according to claim 1, wherein: said power amplifying circuit is of a push-pull arrangement.
Claim 5
Dependent Claim
72 words
An amplifier according to claim 1, wherein: said first power source provides a first power voltage, said second power source provides a second power voltage higher than said first power voltage, and said switch-over means includes diodes connected between said second power source and said drive circuit and between said first power source and said drive circuit both in the forward direction with respect to power source currents through said drive circuit.