Bipolar differential pair based transconductance element with improved linearity and signal to noise ratio

A transconductance circuit comprising:

• a transconductance element with a first and second differential pair of transistors in parallel coupled to a differential input signal, said transconductance element providing a differential current output signal;
• a plurality of diodes coupled to said transconductance element, said diodes for improving linearity of said transconductance element;
• first and second transistors comprising said first differential pair, said first and second transistors coupled differentially to said input signal;
• an emitter of said first transistor, and an emitter of said second transistor coupled to a first node through first and second diodes respectively;
• third and fourth transistors of said second differential pair, said third and fourth transistors coupled differentially to said input signal;
• an emitter of said third transistor, and an emitter of said fourth transistor coupled to a second node through third and fourth diodes respectively;
• a supply voltage coupled to the collectors of said first and third transistors and to the collectors of said second and fourth transistors through first and second current sources respectively;
• said first differential pair with said first and second transistors having a transistor area ratio of 1:r, and said second differential pair, with said third and fourth transistors coupled in parallel with said first differential pair, having a transistor area ratio of r:1;
• said first differential pair coupled to said first and second diodes having a diode area ratio of 1:r, and said third and fourth diodes coupled to said second differential pair having a diode area ratio of r:1.

A transconductance circuit comprising.

• first, second, third and fourth transistors wherein said first and second transistors are coupled differentially to an input signal with said third and fourth transistors;
• said first and fourth transistors having a transistor area ratio of 1:r.sup.2, and wherein said second and third transistors have a transistor area ratio of r.sup.2 :1;
• emitter of said first transistor coupled to a first transistor of a first differential pair and emitter of said fourth transistor coupled to a second transistor of said first differential pair;
• an emitter of said second transistor coupled to a first transistor of a second differential pair, and emitter of said third transistor coupled to the second transistor of said second differential pair;
• an emitter of said first transistor of said first differential pair and emitter of said second transistor of said first differential pair coupled to a first node through first and second diodes respectively;
• an emitter of said first transistor of said second differential pair and emitter of second transistor of said second differential pair coupled to a second node through third and fourth diodes respectively;
• a supply voltage coupled to the collectors of said first transistor of said first differential pair and said first transistor of said second differential pair, and to the collectors of said second transistor of said first differential pair and said second transistor of said second differential pair through first and second current sources respectively.

A transconductance circuit comprising:

• first, second, third and fourth transistors wherein said first and second transistors are coupled differentially to an input signal with said third and fourth transistors;
• said first and fourth transistors having a transistor area ratio of ##EQU34## and wherein said second and third transistors have a transistor area ratio of ##EQU35## an emitter of said first transistor coupled to a first transistor of a first differential pair and emitter of said fourth transistor coupled to a second transistor of said first differential pair;
• an emitter of said second transistor coupled to a first transistor of a second differential pair, an emitter of said third transistor coupled to the second transistor of said second differential pair;
• an emitter of said first transistor of said first differential pair and an emitter of said second transistor of said first differential pair coupled to a first node through first and second diodes respectively;
• an emitter of said first transistor of said second differential pair and an emitter of second transistor of said second differential pair coupled to a second node through third and fourth diodes respectively;
• a supply voltage coupled to the collectors of said first transistor of said first differential pair and said first transistor of said second differential pair, and to the collectors of said second transistor of said first differential pair and said second transistor of said second differential pair through first and second current sources respectively.

A transconductance circuit comprising:

• a transconductance element with a first and second differential pair of transistors in parallel having transistor area ratios of 1:r and r:1, respectively;
• said first and second pair of transistors coupled to a differential input signal, said transconductance element providing a differential current output signal;
• a plurality of diodes coupled to said transconductance element, said diodes for improving linearity of said transconductance element;
• wherein emitters of said first and second differential pair of transistors are coupled to said diodes, said diodes coupled to said emitters of said first differential pair of transistors having a diode area ratio of 1r, and said diodes coupled to said emitters of said second differential pair of transistors having a diode area ratio of r:1;
• wherein said transconductance element comprises:
• first and second transistors, said first and second transistors coupled differentially to said input signal;
• an emitter of said first transistor and an emitter of said second transistor coupled to a first node through first and second diodes, respectively;
• third and fourth transistors, said third and fourth transistors coupled differentially to said input signal;
• an emitter of said third transistor and an emitter of said fourth transistor coupled to a second node through third and fourth diodes, respectively;
• a supply voltage coupled to the collectors of said first and third transistors and to the collectors of said second and fourth transistors through first and second current sources, respectively.

A transconductance circuit comprising:

• a transconductance element with a first and second differential pair of transistors in parallel having transistor area ratios of 1:r and r:1, respectively;
• said first and second pair of transistors coupled to a differential input signal, said transconductance element providing a differential output signal;
• a plurality of diodes coupled to said transconductance element, said diodes for improving linearity of said transconductance element;
• wherein emitters of said first and second differential pair of transistors are coupled to said diodes, said diodes coupled to said emitters of said first differential pair of transistors having a diode area ratio of 1:r, and said diodes coupled to said emitters of said second differential pair of transistors having a diode area ratio of r:1;
• wherein said transconductance element comprises:
• first and second transistors, said first and second transistors coupled differentially to said input signal;
• third and fourth transistors, said third and fourth transistors coupled differentially to said input signal;
• a supply voltage coupled to said first and third transistors and to said second and fourth transistors through first and second current sources respectively.

A transconductance element comprising:

• a transconductance element with a first and second differential pair of transistors in parallel having transistor area ratios of 1:r and r:1, respectively;
• said first and second pair of transistors coupled to a differential input signal, said transconductance element providing a differential output signal;
• a plurality of diodes having nonidentical areas coupled to said transconductance element, said diodes for improving linearity of said transconductance element;
• wherein said transconductance element comprises:
• first and second transistors, said first and second transistors coupled differentially to said input signal;
• third and fourth transistors, said third and fourth transistors coupled differentially to said input signal;
• a supply voltage coupled to said first and third transistors and to said second and fourth transistors through first and second current sources, respectively.