A high-current very wide-band transconductance amplifier

A novel design approach for a high-current, very-wide-band transconductance amplifier is described. The approach is based on paralleling the input and output of complementary unipolar current-mirror cells. Each cell has a fixed current gain determined by the ratio of two resistors. A differential input voltage-to-current circuit drives the cell array. The design avoids the need for a single low-resistance current-sensing resistor and the attendant problems inherent in such resistors. Although the concept is still under development, a prototype of the cell-based transconductance amplifier was implemented with ten positive and ten negative current cells to gain some experimental familiarity with the approach in addition to providing verification of computer simulation results. The prototype transconductance amplifier is DC coupled, has a 3-dB bandwidth of about 750 kHz, and can deliver up to 35 A RMS (root mean square) at 100 kHz with an output compliance voltage of 5 V RMS. Other important characteristics such as output-load regulation and DC offsets are discussed.<
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