Pseudo differential voltage sense MR preamplifier with improved bandwidth

摘要

A preamplifier and its associated biasing circuitry for connection to a magnetoresistive sensor having a first end and a second end is disclosed. The biasing circuitry properly biases the preamplifier such that the preamplifier can properly read signals from the sensor. The preamplifier includes a first transistor. A base of the first transistor is connected to the first end of the magnetoresistive sensor. An emitter of the second transistor is connected to the emitter of the first transistor. A collector of the third transistor is connected to the collector of the first transistor. A base of the fourth transistor is connected to the second end of the magnetoresistive sensor, while the collector of the fourth transistor is connected to the collector of the second transistor, and the emitter of the fourth transistor is connected to the emitter of the third transistor. The preamplifier further includes a voltage source and a first and a second resistor. The first resistor is connected between the voltage source and the collector of the first and third transistors, while the second transistor is connected between the voltage source and the collectors of the second and fourth transistors. Finally, a first current source is connected between the emitters of the first and second transistors and ground, while a second current source is connected between the emitters of the third and fourth transistors and ground.