Programmable passive inductor
View Patent ↗A programmable passive inductor includes two inductors or coils, each having a self-inductance, magnetically coupled together and having a mutual inductance proportional to a magnetic coupling factor. The relative magnitude of the currents through the two inductors can be dynamically varied, which changes the effective inductance.
1. An amplifier circuit, comprising:
a first multiplier configured to receive input signals, wherein the first multiplier multiplies the signals with a constant;
a second multiplier configured to receive the input signals, wherein the second multiplier multiplies the signals with a variable factor C;
a first differential amplifier coupled to receive output signals from the first multiplier, wherein the first differential amplifier comprises a first and a second inductor in parallel and provides an output for the circuit; and
a second differential amplifier coupled to receive output signals from the second multiplier, wherein the second differential amplifier comprises a third and a fourth inductor in parallel, wherein the first and third inductors are coupled with a coupling factor k and the second and fourth inductors are coupled with a coupling factor k.
2. The circuit of claim 1 , wherein the input signals are alternating currents.
3. The circuit of claim 1 , wherein the variable factor C is varied to change the effective impedance of the circuit.
4. The circuit of claim 1 , wherein the first and second multipliers and the first and second differential amplifiers are the same.
5. The circuit of claim 1 , wherein the constant is unity.
6. The circuit of claim 1 , wherein the first differential amplifier further comprises:
a first voltage source coupled to the first and second inductors;
first and second resistors coupled in series to the first and second inductors, respectively;
first and second transistors coupled in series to the first and second resistors, respectively; and
a first current source coupled to the first and second transistors, wherein the output is between the first resistor and transistor and the second resistor and transistor;
and the second differential amplifier further comprises:
a second voltage source coupled to the second and third inductors;
third and fourth resistors coupled in series to the third and fourth inductors, respectively;
third and fourth transistors coupled in series to the third and fourth resistors, respectively; and
a second current source coupled to the third and fourth transistors, wherein the output is between the third resistor and transistor and the fourth resistor and transistor.