Common mode response effects in differential measurements
| Autor: | Ramon Pallàs Areny, Oscar Casas, Gemma Hornero |
|---|---|
| Přispěvatelé: | Universitat Politècnica de Catalunya. Departament d'Enginyeria Electrònica, Universitat Politècnica de Catalunya. GRUP ISI - Grup d'Instrumentació, Sensors i Interfícies |
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Differential gain
Differential amplifier Enginyeria electrònica::Circuits electrònics [Àrees temàtiques de la UPC] Integrated circuits 02 engineering and technology Common mode gain 03 medical and health sciences Differential measurements 0302 clinical medicine Common-mode rejection ratio Control theory Radio frequency 0202 electrical engineering electronic engineering information engineering Mode response Differential circuits Common-mode signal Electrical and Electronic Engineering Common mode rejection ratio Passband Physics Bandwidth (signal processing) Common mode voltage 020206 networking & telecommunications Conditioners Common Differential signal Circuits integrats 030217 neurology & neurosurgery Voltage |
| Zdroj: | UPCommons. Portal del coneixement obert de la UPC Universitat Politècnica de Catalunya (UPC) |
| Popis: | Differential measurements yield signals that are conditioned by differential or fully differential circuits which output depends on both the differential- and common-mode input voltages. Differential signals carry the desired information but common-mode voltages are a nuisance and their contribution to the output signal becomes an interference which is usually evaluated from the ratio between the respective gains for the differential- and common-mode input voltages, Common-Mode Rejection Ratio (CMRR). Usually, only the modulus of the CMRR is specified for integrated differential amplifiers. In this paper we demonstrate that the common-mode response strongly depends on component tolerance and can be band-pass with gain peaking and positive phase shifts inside the passband of the differential signal. Tolerances as low as ±0.01% cannot prevent phase shifts close to +90°. The presence of positive phase shifts in the common-mode gain can be suspected whenever the modulus of the CMRR decreases for frequencies below the −3 dB bandwidth of the differential gain but cannot be appraised from that modulus alone. Surprisingly, a high CMRR at low frequencies can worsen that effect. Therefore, common-mode effects in differential circuits can be evaluated only from the separate description of the response to differential and common-mode inputs signals. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|