US 5,317,217 AGranted

Universal active filter

AssigneeDeutsche Thomson-Brandt GmbH

InventorsMartin Rieger, Sabine Roth

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Abstract

A universal filter is provided with three inputs Vh, Vb and V1, with one output Vout, with two transconductance amplifiers Gm1, Gm2, with four capacitors mCO, (1-m)CO, CO and LCO and an amplifier K as well as a voltage follower VF. Depending on the connections of the three inputs, the universal filter takes the form of a high-pass or low-pass or band-pass filter or a trap filter or an all-pass or an otherwise active filter. Advantageously, by selection of parameters (e.g., trans-conductance, gain, scaling), the various filter characteristics like quality (Q), slope, median frequency, amplification, etc., may be adjusted. A further advantage is that the low component count of the filter provides improved reliability, reduced cost and facilitates efficient and economic fabrication in discrete or integrated circuit form.

Claims16

Dependent claims

A universal active filter, comprising:

first, second and third inputs (V1, Vb, Vh) and an output (Vout);
said first input (V1) being connected with the non-inverting input of a first trans-conductance amplifier (GM1) having an amplification gm1;
said second input (Vb) being connected, via a first capacitor (mCO), with the output of said first trans-conductance amplifier (GM1), with the non-inverting input of a second trans-conductance amplifier (GM2) having an amplification gm2, as well as with a second capacitor ((1-m)CO);
said third input (Vh) being connected, via a third capacitor (CO), with the output of said second trans-conductance amplifier (GM2), with the input of a voltage follower (VF) having a high-resistance input, and with a feedback capacitor (LCO);
and
said filter output (Vout) being connected to the output of said voltage follower (VF), to the inverting inputs of the two transconductance amplifiers (GM1 and GM2), to the second capacitor ((1-m)CO), as well as to the input of an amplifier (K) having an amplification k and having an output connected to said feedback capacitor (LCO).

3 more elements

Dependencies are inferred from the claim text.