Free class‐AB flipped voltage follower using bulk‐driven technique

Abstract

A new configuration of the flipped voltage follower (FVF) offering class-AB operation is presented. The idea uses a bulk-driven transistor instead of the constant current source of the typical FVF topology. This feature enhances the sourcing capability for class-AB operation and the symmetrical slew rate. The key element is changing the basic structure of the original FVF circuit with no additional devices. A detailed analysis of the circuit and simulations using Spice are presented. The experimental results from a manufactured circuit prototype using CMOS 0.35 μm technology demonstrate the feasibility of the proposal.

Class‐AB level shifted flipped voltage follower cell using bulk‐driven technique

“…Due to the body effect, the threshold voltage of transistor M 2 is considered as V TM2 ≈ 1.2 V ToM2 [29]. The minimum power supply voltage of the proposed circuit can be calculated as…”

“…The condition w Z ≥ GBW ensures that the phase margin of the proposed circuit will be at least 45° [29]. Using (37) and (38), stability condition can be derived as…”

Floating-bulk transistors: An alternative design technique for CMOS low-voltage analog circuits

“…Quasi-floating gate requires a high value resistor, R Large , typically implemented by a single transistor connected to a DC biasing voltage and a capacitor, C i , connected to the AC input voltage in order to work properly. Low voltage analog circuits have been widely improved by using these Bulk Driven [4,5,6,7,8,9,10,11,12,13,14,15,16] and Floating Gate [17,18,19,20,21,22,23,24,25,26,27,28,29,30] techniques, and from them we derive the new technique presented in following section.…”

Class AB flipped voltage follower with very low output resistance and no additional power

“…Others use the voltage variations at node 'x' to provide both sourcing and sinking currents, which gives the circuit symmetric operation. , class AB modification of FVF using b) a floating battery [8], and c) a bulk-driven technique [9]. Also shown is d) the Folded FVF (FFVF) [10], e) the proposed class AB version with very low output resistance, and f) the proposed low-voltage version.…”

“…Fig. 1c shows a bulk-driven technique proposed in [9], where the transistor M3, conventionally used as the current source, has its bulk terminal connected to node 'x'. Variations at this node change the source-bulk voltage of this transistor, VSB3, which gives the ability to provide large sourcing currents at the output.…”