Chopping for over 50 MHz gain-bandwidth product current sense amplifiers achieving input noise level of 8.5 nV/√Hz

Publikation: Beitrag in FachzeitschriftForschungsartikelBeigetragenBegutachtung

Abstract

An accurate, high-speed, fully differential difference amplifier for current sensing utilizing the chopper approach was implemented in a 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. Unlike state-of-the-art solutions, we use a higher chopping frequency in the MHz range due to the bandwidth requirements of the introduced circuits for the latter application, namely, low-side phase-current measurement in motor control circuits. Except the low-pass filter (LPF) effect of the output stage, no additional LPF was integrated in hardware at the output of the circuits. We show that on the other hand a digital LPF, which can be integrated in the field-programmable gate-array (FPGA) logic or microcontroller used for the motor control, offers a higher flexibility in terms of filter design. Weak input signals of only few mV can be reconstructed with a high accuracy. This is demonstrated for a 500 kHz rectangular signal and a chopping frequency of 20 MHz. Note that an input-signal frequency of several hundreds of kHz with harmonics in the MHz region is very challenging for chopper amplifiers. Still, a significant decrease of the input-referred noise is demonstrated, especially cancelling out the 1/f-noise achieving a remaining noise floor of approximately 8.5 nV/√Hz. Overall, the input-referred noise level can be pushed far below 50 μV (root mean square). Moreover, using a quite relaxed second-order Butterworth filter with a 3 dB corner frequency of 1 MHz, input-referred noise levels of 10 μV (root mean square) can be easily achieved at the costs of reduced bandwidth. The lowest achieved input offset is 50 μV. The gain is adjusted by resistive feedback and is approximately 40 dB. Hence, the amplifier is suitable for current sensing in motor control circuits, and a significant reduction of the shunt resistance typically used for this purpose will be possible.

Details

OriginalspracheEnglisch
Seiten (von - bis)4179-4190
Seitenumfang12
FachzeitschriftInternational journal of circuit theory and applications
Jahrgang50
Ausgabenummer12
PublikationsstatusVeröffentlicht - Dez. 2022
Peer-Review-StatusJa

Externe IDs

Scopus 85143249840
unpaywall 10.1002/cta.3402
Mendeley 20c8ace3-6e4f-34ae-9945-4387e1d8ab16

Schlagworte

Schlagwörter

  • Chopper amplifier, Chopping, Current sense amplifier, Fully differential difference amplifier, Low-noise design, Phase-current measurement