Seems a simple enough problem this, and perhaps all that is needed is confirmation of approach (although a better solution always appreciated). So the problem:
I have a 555 based square wave based oscillator (clocked at roughly 900hz 5v p2p) which i need to gate the output to enable/inhibit to the Power Amp section of the design (audio use only). I can't use a specifically clocked PWM output pin on mcu (all in use for other needs).
I don't really have room to push in an AND gate to the output (on the target PCB), so was thinking of a classic emitter follower (npn) with the 'collector' fed by the output of the 555, the 'base' driven by an mcu (arduino 5v) output logic pin, and the output to the power amp taken across the emitter and the emitter resistor. In my mind, on low (from the 555) fed to the collector, the transistor will be off, and the emitter, pulled to low either via the emitter resistor or low oscillator output (depending on Vb logic level from the mcu).
Not spectaculary excited about Vbe drop , but can live with it (if its circa the 0.6v expected).
Anyway the question(s) a) is the right way to proceed or is there a better solution (bearing in mind the small pcb space available and my reluctance to make the space for either a 8pin or 14pon standard logic gate ?
b) is there a different approach for generating a logic enabled 900hz audio tone ? (I found using a nand oscillator with enable fed to the first nand wasn't reliable for fastish logic switching from the mcu - I suspect because of interupting the charge/discharge of the RC network on Gate 2 - but happy to guided).
Hope all this made some sort of sense, have a nasty feeling I am missing an obvious solution to this.