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How to build 1KHz Sinewave Generator

2015-01-01 00:00  
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Simple circuitry, low distortion, battery operated

Variable, low impedance output up to 1V RMS

Circuit diagram

1KHz Sinewave Generator-Circuit diagram


R1 5K6 1/4W ResistorR2 1K8 1/4W ResistorR3,R4 15K 1/4W ResistorsR5 500R 1/2W Trimmer CermetR6 330R 1/4W ResistorR7 470R Linear PotentiometerC1,C2 10nF 63V Polyester CapacitorsC3 100μF 25V Electrolytic CapacitorC4 470nF 63V Polyester CapacitorQ1,Q2 BC238 25V 100mA NPN TransistorsLP1 12V 40mA Lamp (See Notes)J1 Phono chassis SocketSW1 SPST Slider SwitchB1 9V PP3Clip for 9V PP3 Battery

Circuit description:

This circuit generates a good 1KHz sinewave using the inverted Wien bridge configuration (C1-R3 & C2-R4). Features a variable output, low distortion and low output impedance in order to obtain good overload capability. A small filament lamp ensures a stable long term output amplitude waveform. Useful to test the Audio Millivoltmeter, Audio Power Meter and other audio circuits published in this site.


The lamp must be a low current type (12V 40-50mA or 6V 50mA) in order to obtain good long term stability and low distortion.Distortion @ 1V RMS output is 0.15% with a 12V 40mA lamp, raising to 0.5% with a 12V 100mA one.Using a lamp differing from specifications may require a change in R6 value to 220 or 150 Ohms to ensure proper circuit's oscillation.Set R5 to read 1V RMS on an Audio Millivoltmeter connected to the output with R7 fully clockwise, or to view a sinewave of 2.828V Peak-to-Peak on the oscilloscope.With C1,C2 = 100nF the frequency generated is 100Hz and with C1,C2 = 1nF frequency is 10KHz but R5 is needing adjustment.High gain transistors preferred for better performance.

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