1222 Tuner VCO Module

[analogoutput]

That’s because of the design of the 3340 chip, see

1222 Tuner VCO Module

Yeah, pulse is +Vcc minus voltage drop over the output transistor (which depends on current, but is nominally +Vcc−1.5V), while triangle output is fixed at +Vcc/3 (so 4 V with a 12 V supply) and any non-trivial load will affect the tuning (so you really want a buffer on that one). Ramp/sawtooth is +Vcc×2/3 (8 V), with more internal buffering. (there may be an argument for turning triangle or ramp into PWM outside the chip to make things more stable, cf the AS3340-HYB variant discussed here, but…

and

1222 Tuner VCO Triangle Waveform Output Volume

Actually the 3340 is a triangle core oscillator, so the saw and pulse are made from the triangle. Saw I think by switching between original triangle and inverted, and pulse by using a comparator. Result (from the datasheet): [image] (Not sure why the saw amplitude is double the triangle, the linked tri to saw method gets you the same amplitude.)

and the 3340 datasheet.

The pulse wave in particular has a larger maximum level than some modules expect — the peak to peak difference is fairly OK, but it’s 0 to 10.5 V rather than centered on zero — so might need attenuation going into them.

There are 3340 VCO designs out there that add gain/offset stages to make all waveforms the same amplitude, and remove the DC level, so they’re all ±5 V. But the 1222 isn’t one of them.