JAJSUV8A June 2024 – November 2024 DAC80516
PRODUCTION DATA
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The transfer function of the output voltage is given by Equation 4.
The resistance values can be chosen so that the quiescent current is negligible compared to the load current. For a desired load current of 10A at a desired VOUTPUT of 5V (with VDAC = 2.5V), choose R1 and R2 as 10kΩ each. This minimizes the quiescent current through the feedback network as 5V / 20kΩ = 250μA.
The base current, IB, for the transistor for a given load current IL is given by Equation 5.
Where:
VOUTPUT / (R1+R2) is equal to the previously calculated quiescent current, which is negligible compared to the load current (particularly for load currents above 1A). This simplifies the equation to Equation 6.
To keep IB less than 20mA, HFE must be greater than IL / 20mA. In general, compensation capacitor C1 is not set by fixed equations, but rather by choosing values while observing the output small-signal step response.