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Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor ma

Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor may be used in a wide variety of applications, including but not limited to use with microfluidic devices for determining particle characteristics such as position, velocity, size, and concentration as well as detection of bacterial spores and other biological agents of potential use in warfare and bio-terrorism.

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Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor ma

Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor may be used in a wide variety of applications, including but not limited to use with microfluidic devices for determining particle characteristics such as position, velocity, size, and concentration as well as detection of bacterial spores and other biological agents of potential use in warfare and bio-terrorism. mparator circuit that generates a switch control signal responsive to a comparison of the voltage on the capacitance and a threshold voltage; and a second switching circuit that selectively couples the secondary winding to the power transfer network responsive to the switch control signal. 8. An apparatus according to claim 7, wherein the power transfer circuit, the feedback circuit and the modulator circuit form a buck regulator. 9. An apparatus according to claim 7, further comprising a feedforward circuit that generates the threshold voltage responsive to a voltage applied to the primary winding of the transformer. 10. An apparatus according to claim 7, wherein the switch control signal comprises a first switch control signal, and wherein the second switching circuit comprises: a first switch that operates responsive to a second switch control signal; a second switch that operative responsive to a third switch control signal; and a complementary driving circuit that generates the second and third switch control signals responsive to the first switch control signal such that the first and second switches operate in a substantially complementary fashion. 11. An apparatus according to claim 10, wherein the complementary driving circuit includes a monostable driving circuit that generates the third switch control signal. 12. A power converter apparatus, comprising: a power transfer network; a transconductance amplifier circuit, coupled to an output port of the power transfer network, that generates a current proportional to a difference between a voltage sense signal representative of an output voltage at the output port and a reference voltage; a capacitor, coupled to the transconductance amplifier circuit, that charges responsive to the generated current; a discharge circuit that intermittently discharges the capacitor; a comparator circuit, coupled to the capacitor, that generates a switch control signal responsive to a comparison of a voltage on the capacitor to a threshold voltage; and a switching circuit, coupled to the comparator, that selectively couples a power source to the power transfer network responsive to the switch control signal. 13. An apparatus according to claim 12, further comprising a second transconductance amplifier circuit, coupled to the output port of the power transfer network, that generates a second current responsive to a comparison of a current sense voltage representative of an output current derived from the output port of the power transfer network to a second reference voltage, and wherein the capacitor is coupled to the second transconductance amplifier circuit and charges responsive to the second current. 14. An apparatus according to claim 12, wherein the power source comprises a secondary winding of a transformer. 15. An apparatus according to claim 14, further comprising a feedforward circuit that generates the threshold voltage responsive to a voltage applied to a primary winding of the transformer. 16. An apparatus according to claim 14, further comprising a second switching circuit that selectively couples a primary winding of the transformer to a voltage source responsive to a second switch control signal, and wherein the discharge circuit intermittently discharges the charged capacitance responsive to the second switch control signal. 17. An apparatus according to claim 12, wherein the switch control signal comprises a first switch control signal, and wherein the switching circuit comprises: a first switch that operates responsive to a second switch control signal; a second switch that operates responsive to a third switch control signal; and a complementary driving circuit that generates the second and third switch control signals responsive to the first switch control signal such that the first and second switches operate in a substantially complementary fashion. 18. An apparatus according to claim 17, wherein the complementary driving circuit includes a monostable driving circuit that generates the third switch control signal. 19. An apparatus according to claim 12, wherein the comparator circuit and the switching circuit couple the power circuit to the power transfer network for intermittent intervals that are initiated responsive to a comparison of the voltage on the capacitor to the threshold voltage. 20. An apparatus according to claim 12, wherein the comparator circuit and the switching circuit couple the power circuit to the power transfer network for intermittent intervals that are terminated responsive to a comparison of the voltage on the capacitor to the threshold voltage. 21. A method of operating a power converter apparatus comprising a transformer having primary and second windings, a modulator circuit operative to couple and decouple a power source to and from the primary winding, and a power transfer network configured to be coupled and decoupled to and from the secondary winding, the method comprising: generating a current responsive to an output voltage at an output port of the power transfer network; charging a capacitance responsive to the generated current; generating a control signal from the modulator circuit; intermittently discharging the capacitance responsive to the control signal; and transferring power from the secondary winding of the transformer to the power transfer network responsive to a voltage on the capacitance. 22. A method according to claim 21, wherein generating a current responsive to an output voltage at an output port comprises generating the current responsive to a comparison of the output voltage to a reference. 23. A method according to claim 22, wherein generating the current responsive to a comparison of the output voltage to a reference comprises generating the current proportional to a difference between a reference voltage and a voltage representative of the output voltage. 24. A method according to claim 21, further comprising generating a second current responsive to an output current derived from the output port to charge the capacitance responsive to the second current. 25. A method according to claim 24, wherein generating a second current responsive to an output current derived from the output port to charge the capacitance responsive to the second current comprises generating the second current responsive to a comparison of the output current to a reference. 26. A method according to claim 25, wherein generating the second responsive to a comparison of the output current to a reference comprises generating the second current responsive to a comparison of a voltage representative of the output current to a reference voltage. 27. A method according to claim 21, wherein transferring power from the secondary winding to the power transfer network responsive to a voltage on the capacitance comprises: generating a switch control signal responsive to a comparison of the voltage on the capacitance and a threshold voltage; and selectively coupling the power source to the power transfer network responsive to the switch control signal. 28. A method according to claim 27, comprising operating the power transfer circuit as a buck regulator. 29. A method according to claim 27, further comprising generating the threshold voltage responsive to a voltage applied to a primary winding of the transformer. 30. A method according to claim 27, wherein the switch control signal comprises a first switch control signal, and wherein selectively coupling the power source to the power transfer network responsive to the switch control signal further comprises: operating a first switch responsive to a second switch control signal; operating a second switch responsive to a third switch control signal; and generating the second and third switch control signals responsive to the first switch control signal such that the first and second switches operate in a substantially complementary fashion. 31. A method according to claim 30,