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.

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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