| 摘要 |
An internal impedance dependent amplifier has an amplification which is determined by the impedance at a given point in the amplifier. A p-i-n diode 42 is connected to the predetermined point 26. The p-i-n diode 42 is powered by a current Ip in the flow direction, which current constitutes the precise amplification control signal for the amplifier. In a preferred embodiment the p-i-n diode 42 is driven by an operations amplifier 56 in such a way that the impedance connected to the given point in the amplifier in this way is temperature dependent. As the p-i-n diode has an impedance expressed by log R = A + B log Ip, where R is the impedance of the p-i-n diode, Ip is the current in the flow direction and A and B are constants which are different for each p-i-n diode, the voltage Vc which is applied to the operations amplifier 56 which drives the p- i-n diode 42, is linear in relation to the impedance of the p-i-n diode 42 and thereby in relation to the voltage amplification in the impedance controlled amplifier to which the p-i-n diode is connected. This characteristic of the amplification in the amplifier makes it possible to cascade connect amplifiers A1 ... A11 and retain the same impedance ratio as expressed above for a cascade connection of amplifiers. The amplification in dB for the cascade connected amplifiers is thus log-linear in relation to a common control voltage, which is applied to each individual amplifier in the cascade connection. <IMAGE>
|
