Positive feedback technique for DC-gain enhancement of folded cascode Op-Amps

Abstract

In this paper, a novel folded cascode operational amplifier is proposed which improves DC-gain using positive feedback technique. This method does not affect the unity-gain frequency, stability, power dissipation, and output voltage swing of the conventional folded cascode Op-Amp. The proposed OpAmp was designed in a standard 0.18µm TSMC 1.8V CMOS technology. Simulation results show a DC-gain enhancement of 25dB and 513MHz unity gain bandwidth for the presented OpAmp. HSPICE simulation results confirm the theoretical estimated improvements.

A Novel MDAC Suitable For A 14B, 120MS/S ADC, Using a New Folded Cascode OP-AMP

“…The output resistance (R O ) in Figure 3(b) is equal to R up || R down . By considering r eq =rds I || rd f || rds 10 , where rd f =rds f + R, and considering By ignoring rds 8 and r eq in comparison with gm 8 r eq rds 8 and Gm f r eq in comparison with Gm f gm 8 r eq rd 8 and considering gm 8 r eq rds 8 =A , and simplifying the value of Gm f , to the value of 1/R , (5) is simplified to (6) .…”

“…However the bulk driven topologies still suffer from the reduction in g mb /g m problem especially in the nanometer CMOS technologies. The final method used to increase the gain is the positive feedback technique [6][7] [8]. However, the gains of the most positive feedback circuits are strongly depend on transistor matching, which causes nonlinearity in the circuit.…”

84 dB DC‐gain two‐stage class‐AB OTA

“…The requirement of portability places some restrictions on the size, weight, and power of the IC. The operational trans-conductance amplifier (OTA) is one of the most widely used building blocks in analog design [1][2][3][4][5][6][7][8]. OTA can be used in low-voltage, low-power, and high-speed applications such as continuous-time Gm-C filters, switched-capacitor circuits, data converters, biomedical implants, signal conditioning of sensors, voltage regulators, and RF receivers [9][10][11][12][13][14][15][16][17][18][19][20].…”

Positive feedback technique and split‐length transistors for DC‐gain enhancement of two‐stage op‐amps

“…In other methods [19, 20], DC‐gain enhancement is obtained with the cost of UGBW decreasing. In [21], a folded cascode op‐amp has been proposed which improves DC gain using positive feedback technique. However, this method is sensitive towards process variation.…”