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push pull driver does not work

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wormux29

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Hi All.

I made circuit as shown in picture. Output signal is connected trough resistor to base of transistors. The waveform at the output is correct but signal amplitude is 9V. I expected amplitude equal 24V. Could you please help me a litle bit. Why it dose not work :)

I will be grateful for any help you can provide.

Best regards.

 

Hi,

The output voltage can not be larger than the input signal voltage at the base.
It is a current amplifier only, but no voltage amplifier.

Klaus
 
You need a driver with level translation, more than two transistors are required to make it. Why don't you use an off-the-shelf integrated driver like TC427?
 

Hi.

Klaus you thinking about something like in picture below?

 

Hi,

With mosfets it is the same. In this circuit they amplify current only.

A simple solution could be an extra npn and a base current limiting resistor.

-->
Disconnect line between port and your_bases.
New npn, emitter to gnd, base with series resistor to port.
Collector to your_bases, pullup to 24V.


Klaus

- - - Updated - - -

Hi,

Almost correct...

Collector to your_bases, pullup to 24V.
Click to expand...

Means: drect connection between collector and your_bases, witout resistor.
AND pullup resistor form collector to 24V.
AND no resistor in emitter path

Klaus
 

Hi.

Many many Thanks :) so the final version can looks like this? Is it right now :)

 

Hi,

looks good.

Maybe you face some problems:

If you need more source current then decrease R2.
If the output_voltage_low of the NE555 is too high, then add a 10k at B and E of T1 (to safely switch T1 OFF).

Klaus
 
One more time thank you, it was very helpful. I'll try this circuit. Is it good practise to always use additional resistor between B and E.
 

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