Protected amplifier apparatus

DETAILED DESCRIPTION In FIG.
1, an input lead 10 provides RF signals to an ALC (automatic level control) block gain control means or feedback controller 12.
This controller has the fast attack, slow decay characteristic common to ALC controllers.
The RF signals may be injection carrier signals for the purpose of tuning the device or may be the modulated signals which include intelligence for radio transmission to a receiver.
An output of the ALC block is supplied on a lead 14 to an RF amplifier 16.
A control input to ALC block 12 is provided on a lead 18 and, thus, the input signals on input 10 are modified in amplitude in accordance with the input on 18 before they are output on lead 14.
RF amplifier 16 provides a signal output on lead 20 to a low-pass filter 22 which supplies signals on a lead 24 to a directional wattmeter 26.
As illustrated, RF amplifier 16 provides a sense signal on a lead 28 to a dash line block 30, including a collector voltage detector 32 and a diode 34.
The signals on lead 28 represent the instantaneous voltage on the collectors of the output stage of the amplifier and these signals are used to provide an indication of high induced voltages which could cause voltage breakdown of the output transistors.
A sense lead 36 from RF amplifier 16 provides a signal indicative of the instantaneous current input to the output devices of RF amplifier 16 and is applied to an average input power detector 38.
Average input power detector 38 receives the input power from a power supply terminal 40.
Output signals from average input power detector 38 are supplied to a subtraction circuit (also termed a dissipation detector) 42 which has an output applied through a diode 44 and then applied to a lead 46.
A switch generally designated as 48 will supply the signals back to lead 18 when the switch 48 is in the TIP condition.
As shown, it is in the TIP condition.
Directional wattmeter 26 supplies output signals to a switch generally designated as 50 which is another stage of switch 48 which is connected by a lead 52 to a third switch 54