sinewave to ttl converter for frequency counter

[neazoi]

Hello, I am making a 0-50MHz MCU frequency counter. The MCU probably accepts ttl levels on it's input and I would like to build a suitable amplifier that will be able to amplify low signal levels and at the same time square them.

I have found two such amplifiers:

**broken link removed**
**broken link removed** (the differential transistor or the line receiver version)

Could you please notify me which is best (and wideband down to DC) or propose a siotable circuit?

 

[captainshahid]

use 74hc14 it is a hex schimitt trigger ic
you can apply any waveform in the input e.g. sine, triangluar , sawtooth , and ouput will be only square wave TTL LEVEL.**broken link removed**

 

[neazoi]

use 74hc14 it is a hex schimitt trigger ic
you can apply any waveform in the input e.g. sine, triangluar , sawtooth , and ouput will be only square wave TTL LEVEL.**broken link removed**

Yes this does the waveform conversion part but only this. To drive a TTL frequency counter you also need preamplification prior to converting, in order low level signals to come to a level suitable for the 7414.

The approach he uses **broken link removed** uses a line driver which i think is very sensitive to voltage variations above or below ground and it can be matched to 50 ohms, which is the standard impedance in RF

I would like your comments on this.

 

[jayanth.devarayanadurga]

This might help you. https://embedded-lab.com/blog/?p=1953

 

[captainshahid]

see this link and you will find everything you want
https://electronics-diy.com/50MHz_Frequency_Meter_Counter.php

 

[neazoi]

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This might help you. https://embedded-lab.com/blog/?p=1953

This amplifier uses a pait of antiparallel diodes as a limiter to "create" the square wave signal at 0.7vpp and then amplifies that to logic levels. This is not a so good technique as it limits very much the sensitivity of the counter! Also It does not seem quite broadband.