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Monday, November 3, 2014

HARTLEY OSCILLATOR

The Hartley Oscillator is characterised by an LC circuit in its collector. The base of the transistor is held steady and a small amount of signal is taken from a tapping on the inductor and fed to the emitter to keep the transistor in oscillation. The transformer can be any speaker transformer with centre-tapped primary. The frequency is adjusted by changing the 470p.

Saturday, August 23, 2014

Triangular Wave Oscillator Wiring diagram Schematic

This design resulted from the need for a partial replacement of the well-known 8038 chip, which is no longer in production and there fore hardly obtainable.

An existing design for driving an LVDT sensor (Linear Variable Differential Transformer), where the 8038 was used as a variable sine wave oscillator, had to be modernised. It may have been possible to replace the 8038 with an Exar 2206, except that this chip couldn’t be used with the supply voltage used. For this reason we looked for a replacement using standard components, which should always be available.

Circuit diagram :

Triangular Wave Oscillator Circuit Diagram

In this schema two opamps from a TL074 (IC1.A and B) are used to generate a triangular wave, which can be set to a wide range of frequencies using P1. The following differential ampliﬁer using T1 and T2 is conﬁgured in such a way that the triangular waveform is converted into a reasonably looking sinusoidal waveform. P2 is used to adjust the distortion to a minimum.

The third opamp (IC1.C) is configured as a difference ampliﬁer, which presents the sine wave at its output. This signal is then buffered by the last opamp (IC1.D). Any offset at the output can be nulled using P3.

Source by : Streampowers