An electronic circuit including an amplifier, a first variable capacitance and a second variable capacitance. The amplifier receives an input signal across an inverting input terminal of the amplifier and a non-inverting input terminal of the amplifier. The first variable capacitance is electrically directly connected to the output terminal of the amplifier and the inverting input terminal of the amplifier. The second variable capacitance is electrically directly connected to the output terminal of the amplifier and the non-inverting input terminal of the amplifier.