Simple LFO update 1.1

New revision for the Simple LFO. It’s mostly a slight improvement of the output stage.

I added an buffering opamp on the output. Now, the output load doesn’t affect and modify anymore the signal frequency.

This is an outdated version, an update is available!

The core oscillator is unchanged:

It’s the classic 2 op amp configuration. The first part (U1A, R1..R4, C1, C2) is an integrator circuit. The second part (U1B, R5..R8) is a schmitt trigger comparator.
U1A output produces the alternating “ramp” signal, giving us the “triangle” signal while U1B output is a square wave signal, 90° phase shifted.
The frequency range is selected by switch (or jumper) S1.

Here’s the new output stage:

U1C is a non inverting amplifier. The optional potentiometer R9 allows you to adjust (reduce) the output signal. The amplification gain is A = 1 + (R10 / R11).

The LED driver is different. Now it’s an op amp instead of a transistor:

The PCB is 5×5 cm wide.

Here are some pictures showing a double eurorack LFO:

Front panels

I made two panels with FPE:

Eurorack 6HP double LFO panel

Eurorack 4HP simple LFO panel

As usual, you’ll find bare PCBs, complete kits and fully assembled and tested modules on tindie!

I sell on Tindie


LFO 1.1 BOM & doc 20161215
LFO 1.1 BOM & doc 20160204
Complete LFO V1.1 schematics (20151120)
Double LFO 6HP Front Panel Express (20150617)
Simple LFO 4HP Front Panel Express (20160205)

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