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Title: Protective circuit for transistor amplifier
Claims: I claim as my invention: 1. A transistor amplifier protective circuit comprising: an input terminal supplying an input signal to said transistor amplifier, a first transistor with its emitter-collector electrodes connected between ground and said input terminal to short said input signal to ground when said first transistor conducts, a first resistor with one side connected to the output of said transistor amplifier, a load connected between ground and the other side of said first resistor, second and third transistors with the collectoremitter path of said second transistor connected between the output of said transistor amplifier and the control electrode of said third transistor, a first capacitor connected between the control electrode of said second transistor and the output of said transistor amplifier, a fourth transistor with its control electrode connected to the emitter-collector path of said third transistor, a bias voltage of a first polarity, and the emitter-collector path of said fourth transistor connected between the control electrode of said first transistor and said bias voltage of a first polarity, a second capacitor connected between said bias voltage of a first polarity and the control electrode of said fourth transistor, a second resistor connected between ground and the control electrode of said fourth transistor, a third resistor connected between the other side of said first resistor and the control electrode of said second transistor, and a fourth resistor connected between ground and the control electrode of said second transistor. 2. A transistor amplifier protective circuit according to claim 1 further including a first diode connected between said first and third resistors, a second diode connected between ground and said fourth resistor and said first and second diodes poled to pass current in the same direction. 3. A transistor amplifier protective circuit according to claim 2 including a Zener diode connected between ground and the control electrode of said first transistor, and a bias voltage of a second polarity connected to said control electrode of said first transistor. 4. A transistor amplifier protective circuit according to claim 3 including a thermistor connected between said bias voltage of a first polarity and a tap point on said second resistor. 5. A transistor amplifier protective circuit according to claim 1 including a second transistor amplifier, a second input terminal supplying an input to said second transistor amplifier, a fifth transistor with emitter-collector electrodes connected between ground and said second input terminal and its control electrode connected to the control electrode of said first transistor, a sixth resistor with one side connected to the output of said second transistor amplifier, a second load connected between ground and the other side of sixth resistor, a sixth transistor with its emitter-collector electrodes connected between the control electrode of said third transistor and the first side of said sixth resistor, and a third capacitor connected between the control electrode of said sixth transistor and said first side of said sixth resistor. 6. A transistor amplifier protective circuit according to claim 5 including a fourth diode, a seventh resistor, an eighth resistor and a fith diode connected in series between ground and the second side of said sixth resistor, and the control electrode of said sixth transistor connected to the junction point between said seventh and eighth resistors. Other info: Inventors: Suzuki, Tadao (Tokyo, JA) Application Number: 486319 Filing Date: 1974-07-08 Publication_date: 1976-01-27 Assignee: Sony Corporation (Tokyo, JA) Primary Class(es): 361/91.1 330/207P, 361/79, 361/106 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Shoop, William M. Assistant Examiner: Salce, Patrick R. Attorney: Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson |
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