Abstract: The present invention relates to an AM-FM receiver suitable for integrated circuit fabrication and having improved mode conversion means. The AM-FM receiver had a d.c. coupled IF broadband IF amplifier comprising a plurality of stages of emitter coupled transistor pairs. A d.c. feedback network is provided to balance the individual stages and to generate a control potential for further use in mode conversion. In the FM mode, the IF amplifier operates with a high, stable gain at the FM IF frequency with gain reduction for noise suppression purposes below the FM IF frequency. Frequency dependent noise suppression is provided by a capacitance associated with the degenerative network. In the AM mode, the IF amplifier operates at a controllable, medium gain with the degenerative effect on IF gain restored at the AM IF frequency by the addition of capacity to the degenerative network.

Abstract: Electronic apparatus is disclosed suitable for integrated circuit fabrication and comprising shunt voltage regulation. The electronic apparatus may be a radio receiver which uses an unregulated current source for its supply voltage. The power amplifier of the audio amplifier has a pair of conventional large area push-pull output transistors which are connected in shunt with the supply. In accordance with the invention, shunt voltage regulation of the supply voltage is achieved by sensing a change in the supply voltage using a zener diode for a voltage reference and then altering the idling current in the output transistors in response to changes in current flow through the zener diode. In consequence of increases in idling current, the output stages shift from class B toward class A operation and shunt regulate the supply voltage. The zener diode is arranged to provide both stabilization of the full supply voltage and the centering voltage of the push-pull output amplifier.