Block diagram of the PNNL current controllers. The shaded items are the focus of this article.
Schematic showing voltage source, voltage noise source (NS), QCL, and simplified classic opamp-based current regulator.
Plot of magnitudes of open loop gain G(s), suppression S(s), and noise functions N(s) and M(s) for current regulator using values typical of PNNL controllers.
Power filters for PNNL current controllers. The zeners are 1N5242 500 mW; all other diodes are 1N4004 or equivalent. Electrolytic capacitors marked with an asterisk rather than a plus sign are tantalums.
Noise performance of positive rail power conditioning chain in QCL7. Current controller loaded at 500 mA, positive rail current 230 mA.
Schematic of a regulator block typical of the PNNL controllers. The sense resistor is 5 Ω for the QCL5 and 2.5 Ω for the QCL7. The series pass transistor Q is an IRFZ14 for the QCL5 and an IRFZ24 for the QCL7. Inductor L is typically 100 μH. Amplifier A r is an AD743 in a non-inverting unity gain configuration. Quantities starting with δ represent voltage and current noise, and are discussed in Sec. VI.
Current noise spectral density traces for the QCL5 and QCL7 operating at 500 mA. The measurement noise floor is also shown. The peaking at 1 MHz and subsequent roll-off is the response of the SR560 voltage amplifier.
Response of QCL5 to 100 kHz square wave.
Significant noise terms and their output contributions for the QCL5 operating at 500 mA, and internal case temperature T = 313°K.
Article metrics loading...
Full text loading...