Abstract: A front-end converter circuit may allow devices, e.g. oscilloscopes and digitizers, to receive input signals having a wide range of possible amplitudes while maintaining a high standardized input impedance. The converter may selectively couple, using low-voltage switches, a selected input network of two or more input networks to a virtual ground node, and a selected feedback network of two or more feedback networks to a transconductance stage input. The selected input network and selected feedback network together define a respective input signal amplitude range. The converter may also controllably adjust an AC gain of the converter to match a DC gain of the converter, and selectively couple non-selected input networks to signal ground. Output referred integrated resistor thermal noise may be reduced to a desired value by lowering the value of the transconductance stage coupled across the input of the converter (through an input resistance) and the virtual ground node.

Abstract: A front-end circuit for measurement devices, for example oscilloscopes or digitizers, may implement DC gain compensation using a programmable variable resistance. A MOS transistor may be configured and operated as a linear resistor with the ability to self-calibrate quickly, while compensating for temperature variations. An integrated CMOS-based variable resistor may be thereby used for an analog adjustable attenuator. Master and slave CMOS transistors may be operated in linear mode, and temperature effects on the linear transistors may be compensated for by using an integral loop controller (current controller) configured around the master MOS transistor. Circuits implemented with the compensated variable resistance have a wide range of adjustment with a control voltage, and may be used in the front-end (circuits) of an oscilloscope or digitizer, or in any other circuit and/or instrumentation benefitting from an adjustable attenuator.

Abstract: A front-end converter circuit may allow devices, e.g. oscilloscopes and digitizers, to receive input signals having a wide range of possible amplitudes while maintaining a high standardized input impedance. The converter may selectively couple, using low-voltage switches, a selected input network of two or more input networks to a virtual ground node, and a selected feedback network of two or more feedback networks to a transconductance stage input. The selected input network and selected feedback network together define a respective input signal amplitude range. The converter may also controllably adjust an AC gain of the converter to match a DC gain of the converter, and selectively couple non-selected input networks to signal ground. Output referred integrated resistor thermal noise may be reduced to a desired value by lowering the value of the transconductance stage coupled across the input of the converter (through an input resistance) and the virtual ground node.

Abstract: A front-end circuit for measurement devices, for example oscilloscopes or digitizers, may implement DC gain compensation using a programmable variable resistance. A MOS transistor may be configured and operated as a linear resistor with the ability to self-calibrate quickly, while compensating for temperature variations. An integrated CMOS-based variable resistor may be thereby used for an analog adjustable attenuator. Master and slave CMOS transistors may be operated in linear mode, and temperature effects on the linear transistors may be compensated for by using an integral loop controller (current controller) configured around the master MOS transistor. Circuits implemented with the compensated variable resistance have a wide range of adjustment with a control voltage, and may be used in the front-end (circuits) of an oscilloscope or digitizer, or in any other circuit and/or instrumentation benefitting from an adjustable attenuator.