This is a simple square-wave generator for measuring slew-rate on amplifiers.
It is built on a piece of strip-board and is powered from a 9 V battery.
U1 is a 5 V regulator.
U2 is an astable multivibrator built around a Schimdt-trigger.
U3 is a divide-by-2 that insures a 50% duty-cycle.
The inputs to the unused gates in U2 and U3 must be connected to GND/VCC as shown.
Alternately, 4 of the inverters can be used to increase the available output current.
The 100 nF capacitors must be ceramic types. All other components are non-critical.
The output voltage between OUTA and GND or between OUTB and GND is 4.5 V-pp.
The output voltage between OUTA and OUTB is 9 V-pp.
If the output voltage is too high, reduce the values of R4 and R5.
The output frequency is approximately 0.6 / ( R1 * C6 ) ( 10 kHz with the values shown ).
The output rise/fall times is 35 ns with no load, but will increase with any real-world load.
Fig.2: Amplifier input example.
When driving an amplifier input as shown in fig.2, the rise/fall times measured between the IN and GND terminals are increased to 1.1 µs.
With an amplitude of 4.5 V-pp, this is a slew-rate of 3.3 V/µs ( 0.8 * 4.5 / 1.1 ). This can be increased by reducing the values of R2 and R3.
Fig.3: Photo of finished circuit.
Never apply high level square waves to multi-way loudspeakers. You will burn the tweeters.
This web-page, including but not limited to all text, drawings and photos, is the intellectual property of Poul Petersen, and is Copyright ©.
Reproduction or re-publication by any means whatsoever is strictly prohibited under International Copyright laws.
The author grants the reader the right to use this information for personal use only.
Any commercial use is prohibited without express written authorization from Poul Petersen.
The information is provided on an "as-is" basis and is believed to be correct, however any use of the information is your own responsibility.
This web-site may contain links to web-sites outside Poul Petersen domain ( www.poulpetersen.dk ).
Poul Petersen has no control over and assumes no responsibility for the content of any web-site outside Poul Petersen own domain.
|Copyright © Poul Petersen 1990 - 2018. Last update: 20181111.||Valid HTML!|