| 摘要 |
1,031,447. Paraphase amplifiers. TEKTRONIX Inc. Aug. 19, 1964 [Aug. 19, 1963], No. 33899/64. Headings H3T and H3W. A paraphase amplifier giving a push-pull output from a single input by means of two transistors or tubes connected by a variable resistance between their emitters or cathodes has the range of gain control without unbalance increased by shunting the base/collector or grid/anode of the input transistor or tube with a resistance approximately equal to its emitter or cathode bias resistance. In Fig. 1, a paraphase amplifier has gain control effective by altering the resistance between the emitters of the two transistors, the range of control being increased by the addition of resistor 42. This resistor is of approximately the same value as the emitter bias resistance 30 and is adjusted so that when the network 14 is open-circuited the output at 38 is zero for all values of the input at 36. The operating points of the two transistors are preferably balanced by including a further resistor 44 equal to the emitter bias resistor 32; this may or may not be equal to resistor 30. A single variable resistor may be used to couple the emitters instead of the network 14. The load resistors 26, 28 should be lower in value than the shunt resistors 42, 44. The two transistors can have different supply voltages. Fig. 2 (not shown) describes an equivalent circuit using triode tubes. |
