Sensitive amplifier having a high voltage switch

摘要

This invention provides an amplifier circuit having first and second transistors interconnected by a third transistor which is symmetrically constructed. A current source is selectively connected to the base of the third transistor. When the current source is connected to the base of the third transistor, the third transistor is saturated, forming a very low impedance path between the first and second transistors. However, when the current source is disconnected from the base of the third transistor, the third transistor impedes the voltage breakdown path between the bases of the first and second transistors. The amplifier circuit is particularly useful in an improved compact magnetic media system wherein both the stored signal and the write signal or voltage are applied to the bases of the first and second transistor of the amplifier without the high write voltages destroying the high performance first and second transistors.