Square Wave Generator


Posted on Feb 4, 2014

One is in good shape, made in 1979, and capable of producing sine, triangle and square waveforms. This one is retained and used as main function generator for testing purposes at my main office location. Other three were not working, or working sporadically. They were all from 1950-ies or early 1960-ies, with electron tubes, of two different types. High voltage was ok on all of them,


Square Wave Generator
Click here to download the full size of the above Circuit.

but output was lacking or intermittent. I decided to scrap them, keep the working tubes, transformers and metal for future projects, and make a new function generator using only transistors. This new generator will be used in the machine shop location. New generator was supposed to have all the bells and whistles, and use case and if possible other parts from the scrapped vacuum-tube generators. Transistor-only design might seem strange at this day and age. However, I wanted to challenge myself. And there was another, somewhat nostalgic reason: I have spent some years in a war zone, and I can appreciate how difficult it is to extract chips from boards (and get their datasheets) during times of war. Transistors were easily removed from equipment, and were not critical when in different role. BC108 will work just as well as 2N2222 in a LF amplifier for instance - often without any change in external components. Therefore, transistor design has a practical second and third world use, IC based one much less so. No special chip Tough luck. It`s not going to arrive on a mortar round. So, for all the people in the world that are maybe now in the similar situation that I was some 20 years ago, it is going to be a simple and reliable, no frills build. Use of a voltage regulator IC is not cheating. Device works perfectly well without it, frequency is just more stable with regulator. Frequency drift using unregulated power supply is...




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