Abstract: A variable capacitor modulator for use in a voltage controlled oscillator, includes a differential varactor block, coupling capacitors for connecting nodes of the varactor block to a tank circuit, and an element connected between the respective nodes and ground to trim the gain of the variable capacitor modulator.

Abstract: A mixer circuit arrangement 30 comprises a complementary transconductor circuit 31 and a mixer stage 32. The complementary transconductor circuit 31 includes two paths in parallel between a positive supply voltage VDD and ground G and is connected directly between the voltage supply terminals VDD and G. The first path includes a P-type MOS transistor TP1 and an N-type MOS transistor TN1 connected in series. Similarly, the second path includes a P-type MOS transistor TP2 and an N-type MOS transistor TN2 connected in series. The gate electrodes of the P-type transistors TP1 and TP2 are connected to a voltage bias Vbp via high value bias resistors Rb, and the gate electrodes of the N-type transistors TN1 and TN2 are connected to a second voltage bias Vbn via high value bias resistors Rb. The mixer stage 32 is connected between the output of the complementary transconductor circuit 31 and a load, the load also being connected to one of the supply terminals.

Abstract: A controllable attenuator has an input and an output, and comprises a first resistive element, a first capacitor connected in series between the input and the output, a first controllable shunting transistor connected between the output and a supply terminal via a second resistive element, and a controllable bypass transistor connected between the input and the output. The controllable attenuator may form part of a radio receiver circuit, the attenuator being positioned between a matching circuit and a low-noise amplifier.

Abstract: A controllable attenuator has an input and an output, and comprises a first resistive element, a first capacitor connected in series between the input and the output, a first controllable shunting transistor connected between the output and a supply terminal via a second resistive element, and a controllable bypass transistor connected between the input and the output. The controllable attenuator may form part of a radio receiver circuit, the attenuator being positioned between a matching circuit and a low-noise amplifier.

Abstract: A mixer circuit arrangement 30 comprises a complementary transconductor circuit 31 and a mixer stage 32. The complementary transconductor circuit 31 includes two paths in parallel between a positive supply voltage VDD and ground G and is connected directly between the voltage supply terminals VDD and G. The first path includes a P-type MOS transistor TP1 and an N-type MOS transistor TN1 connected in series. Similarly, the second path includes a P-type MOS transistor TP2 and an N-type MOS transistor TN2 connected in series. The gate electrodes of the P-type transistors TP1 and TP2 are connected to a voltage bias Vbp via high value bias resistors Rb, and the gate electrodes of the N-type transistors TN1 and TN2 are connected to a second voltage bias Vbn via high value bias resistors Rb. The mixer stage 32 is connected between the output of the complementary transconductor circuit 31 and a load, the load also being connected to one of the supply terminals.