Analog signal processing circuit
View Patent ↗An analog signal processing block with differential signal inputs and including a differential amplifier with differential inputs is disclosed which is configurable to operate either in a differential output mode or in a single-ended output mode without affecting the desired frequency and time characteristics as determined by the switched capacitor networks. The analog signal processing block includes a pair of switched capacitor networks each having one of the differential signal inputs, an input-sided terminal connected to one of the differential inputs of the differential amplifier and an output-sided terminal. The output-sided terminal of a first one of the switched capacitor networks is connected to an output of the differential amplifier. The output-sided terminal of a second one of the switched capacitor networks is connected to a complementary output of the differential amplifier when configured to differential output mode, and connected to a reference potential when configured to the single-ended mode. In this way, an application can use an analog signal processing block in either of the fully differential and single-ended output modes without the need to reconfigure the switched capacitor networks for a desired frequency and time response characteristic.
1. An analog signal processing circuit block with differential signal inputs and including a differential amplifier with differential inputs and configurable to operate either in a differential output mode or in a single-ended output mode;
the analog signal processing circuit block further including a pair of switched capacitor networks each connected to one of said differential signal inputs, an input-sided terminal connected to one of the differential inputs of the differential amplifier, and an output-sided terminal;
wherein the output-sided terminal of a first one of said switched capacitor networks is connected to an output of the differential amplifier; and the output-sided terminal of a second one of said switched capacitor networks is connected to a complementary output of the differential amplifier when configured to operate in the differential output mode, and to a reference potential when configured to operate in the single-ended output mode.
2. The analog signal processing circuit block according to claim 1 , wherein the differential amplifier has two output stages, and one of said output stages is disabled in the single-ended output mode.
3. The analog signal processing circuit block according to claim 2 , wherein the differential amplifier includes an input pair of transistors that have their drains connected to a folded cascode structure with a class AB control block included in each branch of the folded cascode structure, and the class AB control block on the side of the output stage disabled in the single-ended output mode is also disabled in the single-ended output mode.
4. The analog signal processing circuit block according to claim 2 , wherein said output stages each have complementary MOSFET driver transistors and said one output stage is disabled by disconnecting the gates of said driver transistors.
5. The analog signal processing circuit block according to claim 4 , wherein the differential amplifier includes an input pair of transistors that have their drains connected to a folded cascode structure with a class AB control block included in each branch of the folded cascode structure, and the class AB control block on the side of the output stage disabled in the single-ended output mode is also disabled in the single-ended output mode.
6. The analog signal processing block according to claim 1 , wherein the differential amplifier includes common mode feedback circuitry connected in the differential output mode and disconnected in the single-ended output mode.
7. The analog signal processing block according to any of claim 1 , wherein the differential amplifier is configured by application, to the analog signal processing block, of a digital control signal that controls a set of configuration switches associated with the differential amplifier.