Square Wave Generator

Summary/Usage

This device is my DIY square wave generator. It can be used for general purpose measurements in the electronics lab.

Today I use it mostly to test power supplies together with my simple electronic load.

Functional Description

I designed for the following features:

Analog Rotary switches for frequency control
Analog potentiometers for output voltage and offset voltage control
Push button switch with "click" and gold contacts
50 Ohms impedance output jack.

Performance Specs

0.1 Hz - 1 MHz, in steps 1-2-5, crystal oscillator accuracy
Additional always low or always high output with debounced low to high and high to low push button action
Output 10 V_pp max. with 50 Ohm impedance
15 ns rise, 10 ns fall time
Adjustable DC offset
Separate output jack with TTL compatible signal

Design

1 MHz crystal oscillator using one CMOS inverter (well it is a single 74HC00 NAND gate)
Classic TTL 1:10 divider chain using 74LS90 decimal counters plus 1:1, 1:2 and 1:5 dividers, the later also 74LS90
Discrete transistor output stage using a switched current source delivering into a 50 Ohm resistor
Additional adjustable transistor current source to achieve adjustable offset voltage

Schematics (SVG files)

Analog Output Stage Schematics

Digital Part Schematics

LTspice and Kicad files

LTspice and Kicad files can be found in the ZIP-Archive.

Mechanics

Front View

Legal Notices

Copyright

I do not intend to offer/sell this!

I publish here the electrical schematics and the mechanical design, such that you could build your own device. I put all the files of this project under the GPL2 open-source license. See the file COPYING.TXT. This is hence open hardware.

Disclaimer

Actual construction of the circuit requires a significant knowledge of electronic circuit design and construction beyond what is presented here. The author, Dr. Thomas Redelberger, does not warrant operability, reliability, suitability or safety of any of the circuits. Anyone who constructs and/or uses these circuits accepts all responsibility for their operation and safety.