General Engineering Terms
"A" "B" "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M",
"N", "O", "P" "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"

Cosine Wave Oscillator

This circuit is designed to output both a sine wave and cosine wave. This particular design uses an operational amplifier. As shown in the schematic the output frequency is set by the component values as 1Hz. The first operational amplifier outputs a 1Hz sine wave while the second operation amplifier outputs a 1Hz cosine wave. The circuit outputs two sine wave, one 90 degrees out of phase with the other. The two zener diodes are used to set the minimum and maximum voltages. Refer to the link for another Op Amp Sinewave Generator, with a single output.

Sine Wave and Cosine Wave Oscillator circuit
Sine wave / Cosine wave Osc

Of course the primary function of the first op amp is to produce a sine wave, while the second op amp produces the same signal but 90 degrees phase shifted. That is the second op amp uses the sine wave as an input and outputs that signal out of phase [phase shifter].

Component Description

The operational amplifier is a general purpose device, and may be substituted as required. However many of the passive parts set the frequency of operation and should not be substituted, unless a new output frequency is required.

Op Amp: A LM108, general purpose operational amplifier. The most common package style was an 8-pin or 16-pin Plastic DIP Package, or Ceramic DIP Package [military and space applications], an 8-Lead TO-5 Case or a surface mount SOIC Package.

Note the LM108 Op Amp may be discontinued or obsolete, as are the other Temperature Range Variations, LM208 and LM308.
List of Companies making Operational Amplifier ICs. There is an upgrade which may still be stocked as LM108A, although many different op-amps might be substituted for the one in the schematic.

Zener Diode: Reference diode, labeled as 6.3 volts [Vz]. A 6.2v 1N4460 is referenced on this site [5.89v minimum to 6.51v maximum]. Case style is a DO41 Package [Through-Hole].
Companies making Zener Diodes [Switching and Signal Diodes].

Circuit Recommendation

One 30pF capacitor is added between pins 1 and 8 of each Op Amp for frequency compensation. The actual value, although correct for the LM108 may need to change if a different operational amplifier is used. In fact some Op Amp packages don't even have frequency compensation pins, in which case the capacitor would not be required.

One 0.1uF bypass capacitor per voltage supply lead of each Op Amp is used. Low inductance capacitors placed near the body of the device and close to the supply leads is recommended. Short traces between the device and capacitor is also desired.

Depending on the Op Amp used an off-set adjust pin may be offered. However other techniques may be used to shift the output up or down. Refer here for different methods for OpAmp Off-Set Null Adjustment.

PC motherboard

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