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I am designing an astable multivibrator that would avoid rounded output edges and also has a totem pole output, so it is able to drive a small charge pump.

So I decided to replace a collector resistors with bjts.

The “comparators” of C3 and C4 timing capacitor voltages are changed to two current sources against each other.

The output is collectors of Q2 and Q4.

Until now everything works perfect, the output edges have rise/ fall times about 200ns.

But since I need a strong output to drive a charge pump a 22k in bases of Q2 and Q4 doesn’t allow high output current. If I lower these base resistors to get stronger output the shot-through became significant (about 0.5A).

How to overcome this? Is dead time necessary?

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Output waveform (Q2 and Q4 collector):

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Detail of output rise time:

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Try Base Emitter resistors across your proposed strong charge pump PNP /NPN BJTs You could even consider mosfets for the strong charge pump drive or maybe a mosfet driver chip . This will help speed and reduce shoot through .

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  • \$\begingroup\$ There are 330p speed-up capacitors across 22k. They are more effective in speed increasing than BE resistors I think. \$\endgroup\$
    – Michal Podmanický
    Commented Jan 26 at 10:08

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