Implementation and control of filters

An amplifier circuit for use in active filters, said device comprising a first differential gain stage with a first differential input and a first differential output, said first differential gain stage including two amplification components, at least four diode components and a first current generator, said amplification components having substantially equal relationship between current and forward voltage drop, each amplification component having its control electrode connected in counterphase directly to the first differential input, so that the difference between the potentials on the control electrodes increases with increased voltage across the first differential input, said diode components each having substantially the same relationship between current and forward voltage drop as the amplification components, said diode components being series connected in groups so that there are at least two series connected diode components in each group, of which groups a first is connected in series with a first of the amplification components, while a second group is connected in series with a second of the amplification components, said second group including as many diode components as the first group, said first and second amplification components being coupled in counterphase directly to the first differential output, such that the magnitude of the voltage across the first differential output varies with the difference between the forward voltage drops across the first and the second amplification components, further including a third and fourth group of diode components connected in counterphase directly to the first differential output, said fourth group containing as many diode components as the third group, said first current generator being connected to at least one of the amplification components and the groups, such that for an unloaded first differential output the magnitude of the current through the fourth group substantially agrees with the magnitude of the current through the first amplification component, while the magnitude of the current through the third group substantially agrees with the magnitude of the current through the second amplification component.

An amplifier circuit for use in active filters, said device comprising a first differential gain stage with a first differential input and a first differential output, said first differential gain stage including two amplification components, at least four diode components and a plurality of current generators, said amplification components having substantially equal relationship between current and forward voltage drop, each amplification component having its control electrode connected in counterphase directly to the first differential input, so that the difference between the potentials on the control electrodes increases with increased voltage across the first differential input, said diode components each having substantially the same relationship between current and forward voltage drop as the amplification components, said diode components being series connected in groups so that there are at least two series-connected diode components in each group, of which groups a first is connected in series with a first of the amplification components, while a second group is connected in series with a second of the amplification components, said second group including as many diode components as the first group, said first and second amplification components being coupled in counterphase directly to the first differential output, such that the magnitude of the voltage across the first differential output varies with the difference between the forward voltage drops across the first and the second amplification components, further including a third and fourth group of diode components connected in counterphase directly to the first differential output, said fourth group containing as many diode components as the third group, wherein the first amplification component together with the first group of diode components are included in a first series circuit, while the second amplification component together with the second group of diode components are included in a second series circuit, and wherein the first series circuit and the third group of diode components are connected in parallel to a first current generator such that the sum of the currents through the first amplification component and the third group are substantially constant for an unloaded first differential output, and also wherein the second series circuit and the fourth group of diode components are connected in parallel to a second current generator such that the sum of the currents through the second amplification component and the fourth group is substantially constant for an unloaded first differential output, further including a fifth and a sixth group of equal number of diode components connected in parallel to a third current generator such that the sum of the currents through the fifth and the sixth groups is substantially constant, said first series circuit and the fifth group being connected in parallel to a fourth current generator such that the sum of the currents through the first series circuit and the fifth group is substantially constant, and the second series circuit and the sixth group being connected in parallel to a fifth current generator such that the sum of the currents through the second series circuit and the sixth group is substantially constant, and wherein the first, second, third, fourth, and fifth current generators generate substantially equal currents.

An active filter comprising a first differential gain stage with a first differential input and a first differential output, said first differential gain stage including two amplification components, at least four diode components, a capacitive component connected between the amplification components on the opposite side of the respective amplification components as is the differential output of the differential gain stage, and at least one current generator, said amplification components having substantially equal relationship between current and forward voltage drop, each amplification component having its control electrode connected in counterphase directly to the first differential input, so that the difference between the potentials on the control electrodes increases with increased voltage across the first differential input, said diode components each having substantially the same relationship between current and forward voltage drop as the amplification components, said diode components being series-connected in groups so that there are at least two series-connected diode components in each group, of which groups a first is connected in series with a first of the amplification components, while a second group is connected in series with a second of the amplification components, said second group including as many diode components as the first group, said first and second amplification components being coupled in counterphase directly to the first differential output, such that the magnitude of the voltage across the first differential output varies with the difference between the forward voltage drops across the first and the second amplification components, and wherein the first group and second group of diode components are connected in counterphase directly to the first differential output, there being at least one current generator connected to one of the amplification components and the groups, such that for an unloaded first differential output the magnitude of the current through the first group substantially agrees with the magnitude of the current through the first amplification component, while the magnitude of the current through the second group substantially agrees with the magnitude of the current through the second amplification component.