Protection circuit for an amplifier

Claim 2

A protection circuit for an electronic amplifier, including in combination, first amplifier means for amplifying a signal coupled thereto and to be protected, a second amplifier coupled to said first amplifier means for further amplifying the signal amplified by said first amplifier means, power supply means for supplying an operating current and an operating voltage, means forming a current path between said second amplifier and said power supply means for supplying current to said second amplifier from said power supply means, said means including current sensing means connected in series in said current path from said power supply means to a reference potential for sensing the current in said current path and developing a sensing signal which varies in accordance with variations in said current, a control circuit coupling said power supply means to said first amplifier means for supplying said operating voltage thereto, said control circuit having a voltage regulating portion for regulating the operating voltage from said power supply means, and supplying a regulated voltage having a first amplitude to said first amplifier means, said control circuit further having circuit means coupled to said voltage regulating portion and said current sensing means and operative in response to a reduced sensing signal to control said regulating portion to reduce said regulated voltage from said first amplitude to a second, lower, amplitude for operating said first amplifier means at a safe level.

Claim 3

The protection circuit of claim 1 wherein said first amplifier means having at least one state is a semiconductor amplifier.

Claim 4

The protection circuit of claim 2 wherein said second amplifier is an electron tube amplifier.

Claim 5

The protection circuit of claim 3 wherein said current sensing means includes, resistance means connected from said power supply means to said reference potential in said current path, said operating current flowing through said resistance means to develop said sensing signal.

Claim 6

The protection circuit of claim 4 wherein said voltage regulating portion includes, voltage regulating semiconductor means, said semiconductor means having an output electrode coupled to said first amplifier means for supplying said regulated operating voltage to said first amplifier means, an input electrode coupled to said power supply means for receiving said operating voltage therefrom, and a control electrode, a bias circuit, including first bias means, coupled to said control electrode for establishing a bias potential thereat, said semiconductor means operative in response to said bias potential to limit said regulated operating voltage to said first amplitude, said semiconductor means operative in response to a reduction of said bias potential to reduce the regulated operating voltage to said first amplifier to said second amplitude.

Claim 7

The protection circuit of claim 5 wherein said first bias means is a zener diode.

Claim 8

The protection circuit of claim 5 wherein said circuit means includes, a control semiconductor, said control semiconductor having a control electrode coupled to said current sensing means, a first electrode coupled to a reference potential, and a second electrode, second bias means coupled to said second electrode and said control electrode of said voltage regulating semiconductor means, said control semiconductor being responsive to a reduction in said sensing signal below a predetermined level to become conductive and couple said second bias means to said reference potential, said second bias means operative in response to said conduction to reduce said bias potential.

Claim 9

The protection circuit of claim 7 wherein said second bias means is a zener diode.

Claim 10

A protection circuit for an electronic amplifier, including in combination, first amplifier means for amplifying a signal coupled thereto and to be protected, a second amplifier coupled to said first amplifier means for further amplifying the signal amplified by said first amplifier means, power supply means for supplying an operating current and an operating voltage, means forming a current path between said second amplifier and said power supply means for supplying current to said second amplifier from said power supply means, said means including current sensing means connected in series in said current path from said power supply means to a reference potential for sensing the current in said current path and developing a sensing signal which varies in accordance with said variations in said current, a control circuit including a voltage regulating portion having a voltage regulating semiconductor means, said semiconductor means having an output electrode coupled to said first amplifier means for supplying said regulated operating voltage to said first amplifier means, an input electrode coupled to said power supply means for receiving said operating voltage therefrom, and a control electrode, a bias circuit including first bias means coupled to said control electrode for establishing a bias potential thereat, said semiconductor means operative in response to said bias potential to limit said regulated operating voltage to a first amplitude, said semiconductor means operative in response to a reduction of said bias potential to reduce the regulated operating voltage to said first amplifier to a second amplitude, said control circuit further having circuit means coupled to said voltage regulating semiconductor means control electrode and to said current sensing means and operative in response to a reduced sensing signal to reduce said bias potential.

Claim 11

A protection circuit for an electronic amplifier, including in combination, first amplifier means for amplifying a signal coupled thereto and to be protected, a second amplifier coupled to said first amplifier means for further amplifying the signal amplified by said first amplifier means, power supply means for supplying an operating current and an operating voltage, means forming a current path between said second amplifier and said power supply means for supplying current to said second amplifier from said power supply means, said means including current sensing means connected in series in said current path from said power supply means to a reference potential for sensing the current in said current path and developing a sensing signal which varies in accordance with said variations in said current, a control circuit including a voltage regulating portion having a voltage regulating semiconductor means, said semiconductor means having an output electrode coupled to said first amplifier means for supplying said regulated operating voltage to said first amplifier means, an input electrode coupled to said power supply means for receiving said operating voltage therefrom, and a control electrode, a bias circuit including first bias means coupled to said control electrode for establishing a bias potential thereat, said semiconductor means operative in response to said bias potential to limit said regulated operating voltage to a first amplitude, said semiconductor means operative in response to a reduction of said bias potential to reduce the regulated operating voltage to said first amplifier to a second amplitude, said control circuit further having circuit means coupled to said voltage regulating semiconductor means control electrode and to said current sensing means and operative in response to a reduced sensing signal to reduce said bias potential.