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Topic: Frequency Counter - Amplifier / Preamplifier (Read 507 times) previous topic - next topic

arduinoaleman

May 19, 2015, 11:44 pm Last Edit: May 20, 2015, 01:45 am by arduinoaleman
Hi,

if you are looking for a pre-amplifier for your frequency counter, have a look at this circuit.
It works well from 2Hz to more than 20 MHz.

The BF245B is no longer in production, but is still available.

The circuit is shown in the attachment.

The power supply is Arduino compatible (5 Volts).
I have tested the amplifier successfully with signals from 50mV to 5V (TTL).

Have fun.


Sorry, I will not answer any questions concerning the circuit.
I am not using this forum very often.

arduinoaleman

If your questions are not precise, nobody can help you.

arduinoaleman

Please add a 3K3 ohms resistor just behind the 1µ and 100 pf input capacitors. Otherwise the two protection diodes can distort TTL signals (at certain frequencies) to a level where the output is not reliable anymore.

Otherwise the amplifier works perfectly.

If your questions are not precise, nobody can help you.

raschemmel

The General Electronics topic is intended for posts from people seeking help.
This is a helpful post but you are not asking for help. Your post would probably be better in the Exhibition /Gallery, even though that topic is really overkill for this post. Ideally, the forum should have a topic that covers everything in between but not necessarily Exhibition posts. Perhaps a topic called "General Electronics Miscellaneous suggestions and tips" ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

polymorph

#3
Mar 08, 2016, 08:20 pm Last Edit: Mar 08, 2016, 08:21 pm by polymorph
It seems like overkill for only 20MHz. There are a number of MMIC wideband amplifiers that are good to 1GHz, depending on board layout. Around $10 give or take. Or on eBay, 5 for $10 give or take.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - tinyurl.com/q7uqnvn
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

pwillard

Its so  "German"!

I like it, but I also agree that it exceeds what I would need as a front end.

For my usual needs, I'd keep maybe the first FET, level covert it with an emitter follower transistor and feed that to a 74HC14.

MarkT

Please add a 3K3 ohms resistor just behind the 1µ and 100 pf input capacitors. Otherwise the two protection diodes can distort TTL signals (at certain frequencies) to a level where the output is not reliable anymore.

Otherwise the amplifier works perfectly.


Those input diodes will be fried without series resistance too!  I'd suggest 220 ohms so there's
less reflection and better damping.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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