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What is the maximum frequency of CMOS (3.3V) level triangle (or square) wave that I can achieve with serial discrete ICs (for example: discrete PLL or DAC + OpAmp cascade)?

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    \$\begingroup\$ Zero Hz for a pure triangle or square wave. \$\endgroup\$ – Andy aka Mar 28 '20 at 10:53
  • \$\begingroup\$ As Andy indicates, you need to define how triangular your triangle wave needs to be, or how square your square wave needs to be. You typically do that by means of voltage or current slope. That defines the bandwidth your signal needs. Then you compare that to the ICs available. Generally, there's hardly a sensible limit to be given without knowing the rest of your constraints. \$\endgroup\$ – Marcus Müller Mar 28 '20 at 12:13
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    \$\begingroup\$ Really, this question is as much of an XY Problem as it can possibly get. You need to explain what you're trying to build, in the larger scheme of things, before we can reasonably help you. \$\endgroup\$ – Marcus Müller Mar 28 '20 at 12:14
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    \$\begingroup\$ So look for a circuit that has the 3 dB specified (a very common specification indeed). \$\endgroup\$ – Andy aka Mar 28 '20 at 12:51
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    \$\begingroup\$ Arseniy, I really meant that when I said that a reasonable answer requires knowledge of your application. There's certainly wideband amplifiers giving you several GHz of bandwidth, but can still drive up to 3.3V. The question is whether you can design, layout and manufacture a board and casing that allows for such frequencies, not alone whether the ICs exist. Vote to close as lacking important background information. \$\endgroup\$ – Marcus Müller Mar 28 '20 at 13:21
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a single CMOS inverter is an opamp.

you can get such performance (poorly) way past 10,000,000,000 Hz.

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This depends on multiple factors on the components you choose that you can find in the datasheets of the components. Some examples in the case of CMOS are the on and off times (rise and fall time) that can give you an insight on how fast the mosfet can go to 3.3v and 0v and the capacitances around the mosfet which in higher frequencies can act as filters.

In the case of Opamps the slew rate is the most important along with the bandwidth of the op amp which sets the limits on the product of frequency * gain.

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I guess there's well performing GHz range transmitters which can well output for ex. the needed voltage, the limit is at the receiving end. Different CMOS cicuits need differently wide pulse to do their jobs. Check how wide pulses your circuits need, multiple it by 2 and calculate the inverse. That's your frequency.

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