US 5,642,071 AGranted

Transit mixer with current mode input

AssigneeAlcatel

InventorsJoannes Mathilda Josephus Sevenhans, Jean-Luc Donat Maurice R. Bacq, Damien Luc Francois Macq

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Abstract

A differential mixer (DM) used in a telecommunication radio transmitter able to operate with a 3 Volt supply includes a silicon bipolar cross-connected pair of differential amplifiers (A; B) for receiving a first input voltage (LO) at a high frequency, a pair of current sources (I1; I2), and a voltage-to-current MOS converter (VIC) for receiving a second input voltage (VIN) at a lower frequency. The converter is adapted to convert the low frequency voltage to a differential current (INN) and is coupled to the junction points of the amplifiers and the current sources. The converter further includes a regulated differential cascode circuit (P1; P2) to which the low frequency input voltage (VIN) is applied via resistors (RI1; RI2) and which is coupled to the supply terminals (VCC; GND) of the mixer via two pairs of constant current sources (PB1, PB2; NB1, NB2) respectively. Preferably, a constant reference voltage terminal (VCC/2) is applied to the gate electrode of the transistors (P1; P2) of the cascode circuit via an operational amplifier (O1; O2).

Differential mixer (DM) coupled between a first (VCC) and a second (GND) voltage supply terminal for multiplying a first differential input voltage supplied at a first differential voltage input (LO) with a second differential input voltage supplied at a second differential voltage input (VIN), said differential mixer (DM) including a cross-connected pair of differential amplifiers (A;

B) responsive to said first differential voltage input and coupled between said first (VCC) voltage supply terminal and a differential pair of mixing input terminals (J1;
J2) to which are also coupled a voltage-to-current converter means (VIC) and a current source (I1;
I2), said current source including two identical parallel current branches, each connected between distinct differential amplifiers (A;
B) via a distinct mixing input terminal (J1;
J2) and said second (GND) voltage supply terminal, said parallel current branches each comprising a series connection of a transistor (T1;
T2) and a resistor (R5;
R7) and said voltage-to-current converter means responsive to said second differential voltage input for converting said second differential input voltage to a differential current (INN) supplied to said differential mixing input terminals, said voltage-to-current converter means including a differential cascode circuit of transistors (P1;
P2) having input terminals (J3;
J4) to which said second differential voltage input are connected via resistors (RI1;
RI2), output terminals connected to said mixing input terminals which are current output terminals (TI1;
TI2), and control terminals to which a constant reference voltage terminal (VCC/2) is coupled, said voltage-to-current converter means further including a first pair of constant current sources (PB1, PB2) coupling said first (VCC) voltage supply terminal to the input terminals of said transistors, and a second pair of constant current sources (NB1, NB2) coupling the output terminals of said transistors to said second (GND) voltage supply terminal.

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Abstract

Claims9