Current bias, current sense preamplifier for a magnetoresistive reader

A preamplifier system connected to a bias current generator for receiving information from a storage medium via a plurality of dual strip readers comprising a first and a second magnetoresistive element, a first and a second transistor, and a first and a second switch, and for providing an output signal to circuitry external from the preamplifier system, the system comprising:

• a first capacitor connected between a first potential and a base of the first transistor via the first switch;
• a second capacitor connected between the first potential and a base of the second transistor via the second switch;
• a third capacitor connected between the first and second capacitors;
• a first operational amplifier having a positive input, a negative input, and an output, the negative input connected to the bias current generator and the output connected to the base of the first transistor;
• a second operational amplifier having a positive input, a negative input, and an output, the negative input connected to the bias current generator and connected to the negative input of the first operational amplifier, and the output connected to the base of the second transistor;
• and
• a feedback unit connected to the bias current generator, connected to the positive inputs of the first and second operational amplifiers, and connected to the collectors of the first and second transistors.

A preamplifier system for receiving information from a storage medium via a magnetoresistive element and for providing an output signal to circuitry external from the preamplifier system, the system comprising:

• a bias current generator connected to a high potential for providing a bias current to the preamplifier system;
• a first transistor having a base, a collector, and an emitter, the emitter connected to the magnetoresistive element;
• a capacitor connected between the base of the first transistor and a low potential;
• an operational amplifier having a positive input, a negative input, the negative input connected to the bias current generator, and the output connected to the base of the first transistor;
• and
• a feedback unit connected to the bias current generator, the feedback unit comprising:
• a second transistor having a base, a collector, and an emitter, the collector connected to the capacitor;
• a third transistor having a base, a collector, and an emitter, the base and collector connected together and connected to the base of the second transistor;
• a first resistor connected between the emitter of the second transistor and the bias current generator;
• a second resistor connected between the emitter of the third transistor and the bias current generator;
• a fourth transistor having a base, a collector, and an emitter, the base connected to the collector of the third transistor, the collector connected to the positive input of the operational amplifier, and the emitter connected to the collector of the first transistor;
• and
• a third resistor connected between the collector of the fourth transistor and the high potential.

A preamplifier system for receiving information from a storage medium via a magnetoresistive element and for providing an output signal to circuitry external from the premplifier system, the system comprising:

• a bias current generator for providing a bias current to the preamplifier system;
• a first transistor connected to the magnetoresistive element;
• a capacitor connected between the first transistor and an output, the first input being connected to the bias current generator, and the output being connected to the first transistor;
• and
• a feedback unit comprising:
• a first resistor connected between a second fixed potential and the second input of the operational amplifier;
• a second resistor connected to the bias current generator;
• a third resistor connected to the bias current generator;
• a second transistor connected between the first resistor and the first transistor;
• a third transistor connected between the second resistor and the capacitor;
• and
• a fourth transistor connected between the third resistor and the second transistor, the fourth transistor having a control element and a controlled element connected together and connected to a control element of the third transistor.