Transconductor stage for high frequency filters

An integrated circuit, comprising:

• first and second matched current sources, and a third current source;
• first and second matched insulated-gate field-effect transistors (IGFETs), each connected to receive a respective side of a complementary input signal on a gate thereof;
• and
• first and second matched bipolar transistors;
• a current sink controlled to sink a current equal to the sum of said first, second, and third current sources;
• said first IGFET, first bipolar, and first current source all being connected in series, and connected to said current sink, and operatively connected to a first output terminal;
• said second IGFET, second bipolar, and second current source all being connected in series, and connected to said current sink, and operatively connected to a second output terminal;
• a third bipolar transistor which is diode-connected, and connected to sink current from said third current source;
• and
• a voltage source connected between said third bipolar transistor and said current sink;
• said first, second, and third bipolar transistors all having respective bases thereof connected together;
• said first and second current sources each incorporating a respective transistor whose conductivity is modulated by a respective one of said first and second output terminals.

An integrated circuit, comprising:

• first and second mutually matched current sources, and a third current source;
• first and second mutually matched n-channel insulated-gate field-effect transistors (IGFETs), each connected to receive a respective side of a complementary input signal on a gate thereof;
• and
• third and fourth mutually matched IGFETs, each having approximately one-half the channel area of said first IGFET, and
• first and second mutually matched bipolar transistors;
• a current sink controlled to sink a current equal to the sum of said first, second, and third current sources;
• said first IGFET, first bipolar, and first current source all being connected in series, and connected to said current sink, and operatively connected to a first output terminal;
• said second IGFET, second bipolar, and second current source all being connected in series, and connected to said current sink;
• a third bipolar transistor which is diode-connected, and connected to sink current from said third current source;
• and
• a resistor connected between said third bipolar transistor and said current sink;
• said first, second, and third bipolar transistors all having respective bases thereof connected together;
• and
• said third IGFET being connected between the gate of said first IGFET and the drain of said second IGFET, and said fourth IGFET being connected between the drain of said first IGFET and the gate of said second IGFET.

A transconductor differential stage for high-frequency filters, comprising:

• an input circuit portion comprising a pair of MOS transistors having gate terminals connected to receive signal inputs;
• an output circuit portion, comprising a pair of output terminals, and a pair of bipolar transistors each connected in series between a respective one of said MOS transistors and a respective one of said output terminals, said pair of bipolar transistors having their bases connected together:
• and
• an additional pair of MOS transistors, each having respective source and drain terminals connected to a corresponding drain terminal of one transistor in said first pair of input transistors, and a respective gate terminal cross-connected to the gate terminal of the other transistor in said first pair.

A band-pass filter, comprising at least one transconductor stage which comprises:

• an input circuit portion comprising a pair of MOS transistors having gate terminals connected to receive signal inputs;
• an output circuit portion, comprising a pair of output terminals, and a pair of bipolar transistors each connected in series between a respective one of said MOS transistors and a respective one of said output terminals, said pair of bipolar transistors having their bases connected together;
• and
• an additional bipolar transistor having its base in common with said bipolar transistors and its emitter connected to the sources of said MOS transistors via a voltage source.

An integrated circuit continuous-time filter, comprising:

• multiple transconductor stages connected to implement a desired transfer function;
• wherein multiple ones of said transconductor stages each comprise a mixed-technology differential stage which includes:
• first and second matched current sources, and a third current source;
• first and second matched insulated-gate field-effect transistors (IGFETs), each connected to receive a respective side of a complementary input signal on a gate thereof:
• and
• first and second matched bipolar transistors;
• a current sink controlled to sink a current equal to the sum of said first, second, and third current sources;
• said first IGFET, first bipolar, and first current source all being connected in series, and connected to said current sink, and operatively connected to a first output terminal;
• said second IGFET, second bipolar, and second current source all being connected in series, and connected to said current sink;
• a third bipolar transistor which is diode-connected, and connected to sink current from said third current source;
• and
• a voltage source connected between said third bipolar transistor and said current sink;
• said first, second, and third bipolar transistors all having respective bases thereof connected together.