| 摘要 |
PURPOSE:To provide the function of impedance converting and load impedance formation for the titled circuit to be usable at high frequencies, by setting an input impedance of an amplifier with a low gain to a value corresponding to a transfer function. CONSTITUTION:A voltage Ei is applied to an input terminal of an amplifier A having the unity of amplification factor. A feedback element T having a prescribed transfer function H(S) connected to an output terminal of the amplifier A is fed back to the input terminal of the amplifier A via a transistor (TR)Q. A current flowing to the collector in response to the volage EiXH(S) applied to the base of the TRQ is taken as I1+DELTAI2, where DELTAI2 is a current flowing to the collector when the base potential is zero. A current Ii is expressed as Ii=I1+DELTAI2+ I3-I4, where I3 is a current flowing to the power supply through a resistor Rc and I4 is a current flowing to a resistor R1 caused by a potential at a common connecting point J of the resistors R1-R3. Thus, the input impedance Zin is expressed as Zin=Rv/H(S), where Rv can be determined with the R1-R3. |
