Monolithic integratable adjustable impedance

摘要

The impedance involves a first transistor (T1) and a second transistor (T2). The emitters of the transistor are each connected via individual resistors (R1,R2), respectively, to a first terminal (E1) of the adjustable impedance (Z). The base (B) of the first transistor (T1) is connected to the other terminal (E2) of the impedance (Z). The emitter of the first transistor (T1) is connected to a constant current source (I1) which determines the operating point of the first transistor (T1). The collectors of both transistors (T1,T2) are connected to the base of the first transistor (T1). An adjustable voltage source (US) is connected between the bases of both transistors (T1,T2) for adjusting the impedance (Z). A constant current source may be connected to the emitter of the first transistor (T1) via the resistor (R1), leading from the first terminal to the first transistor. The emitter of the second transistor (T2) may be connected to an adjustable current source, which is adjusted together with the voltage source.