A 3 V pseudo-differential transconductor with intrinsic rejection of the common-mode input signal

Abstract

Transconductance differential amplifiers directly r e f e r r e d t o g r o u n d (we will call them "pseudo-differential" structures to distinguish from the fully-differential ones) a r e not intrinsically capable of rejecting the common-mode (CM) input signal. This paper deals with the problems related to the propagation of t h e CM signal in differential circuits. A new pseudo-differential transconductor architecture with a high Common-Mode Rejection Ratio (CMRR) is proposed. The novel structure is based on a transconductor sensible only to CM signals which is added in parallel to the original one, in order to implement a feed-forward cancellation of the CM output signal current. An efficient circuital implementation of this struct u r e is presented. Comparative simulations demons t r a t e t h a t the proposed technique is competitive with the classical fully-differential one particularly a t high frequency when the CMRR rapidly degrades.

An Ultra-Low Voltage Analog Front End for Strain Gauge Sensory System Application in 0.18µm CMOS

“…As a building block for the filter, a pseudo-differential amplifier with common-mode feedforward (CMFF) [4] shown in Fig. 16 is used in this design.…”

“…With V dd of 0.6 V, the use of tail current source reduces the available headroom for the input and active load transistors. Tail current source-less design or pseudo-differential [4], although very attractive in low V dd design, has poor common-mode rejection (CMR) which is not adequate for instrumentation application. Cascading fully differential amplifiers can solve this problem at the cost of higher power consumption.…”

Low‐power, high‐linearity transconductor with a high tolerance for process and temperature variations

“…Also, there are many reports about the low‐power design of the CMOS transconductor. The most popular low‐power topology of the transconductor is the pseudo‐differential pair [13, 28, 29]. However, the pseudo‐differential structure usually has poor rejection of common‐mode signals, which therefore can originate a large amount of distortion.…”

“…The common‐mode feedback circuit can overcome this drawback, but it increases both noise and power consumption. Although the technique for common‐mode signals cancellation has been used, the CMRR performance of the pseudo‐differential transconductor is inferior to the classical fully differential one particularly at low frequency [28].…”

A highly linear CMOS pseudo differential transconductor using active attenuator

“…The FDTA is typically based on source coupled differential pair with a tail current source and the PDTA consists of two single input transconductors; that without current bias source. Because of which, it is also known as ground referred differential pair [5,6]. The voltage drop across the tail current source present in FDTA is reduced to zero in PDTA; more voltage headroom for output [7,8].…”