Rail-to-Rail Buffer Amplifier with Adaptive Biasing for Flat Panel Displays

Flat panel displays require buffers for column driving circuits. These buffers have unity gain and usually drive large capacitive loads. To maintain the railto-rail swing operation, most of the buffer circuits employ complementary differential pair input stage. Whenever the input voltage is close to supply voltages, one of the driving paths enters the cut-off state. In this paper, a novel adaptive biasing technique for biasing differential input pair transistors is proposed in order to maintain high driving capacity for the whole input range. In the proposed scheme, whenever an NMOS input stage enters the cut-off stage, the biasing current is boosted for the PMOS input stage and vice versa. As a result, without increasing the biasing current, driving capability of the circuit is boosted in the ranges which are close to the supply voltages. With the proposed biasing scheme, the circuit consumes 45% less biasing current with 16% better settling time as compared to the non-adaptive biased circuit. The proposed biasing circuit and liquid-crystal displays (LCD) buffer is designed using 0.35 µm AMS technology and the SPICE results are reported. The circuit provides high slew-rate and good settling time characteristics which is comparable to the state-of- art LCD driving circuits.

PDF

___

1. Chih-Wen Lu and Kuo-Jen Hsu, “A high-speed low-power rail-torail column driver for AMLCD applications,” IEEE J. Solid State Circuits, vol. 39, no. 8, pp. 1313–1320, Aug. 2004.
2. Pang-Cheng Yu and Jiin-Chuan Wu, “A class-B output buffer for flat-panel-display column driver,” IEEE J. Solid State Circuits, vol. 34, no. 1, pp. 116–119, Jan. 1999.
3. D. J. R. Cristaldi, S. Pennisi and F. Pulvirenti, Liquid Crystal Display Drivers: Techniques and Circuits. Berlin: Springer, 2009.
4. J. S. Kim, J. Y. Lee and B. D. Choi, “Slew-rate enhanced rail-to-rail buffer amplifier for TFT LCD data drivers,” Electron. Lett., vol. 48, no. 15, Jul. 2012.
5. T. Itakura and H. Minamizaki, “A two gain-stage amplifier without an on-chip Miller capacitor in an LCD Driver IC,” IECE Trans. Fundamentals, vol. E85-A, no. 8, pp. 1913–1920, Aug. 2002.
6. M. Yildiz, S. Minaei and E. Arslan, “High-slew rate low-quiescent current rail-to-rail CMOS buffer amplifier for flat panel displays,” J. Circuits Syst. Comput., vol. 20, no. 7, pp. 1277–1286, 2011:
7. D. Marano, G. Palumbo and S. Pennisi, “A new compact low-power high speed rail-to-rail class-B buffer for LCD applications,” J. Disp. Technol., vol. 6, no. 5, May, 184–190.
8. A. Sedra and K. Smith, Microelectronic Circuits, 7th ed. Oxford: Oxford University Press, 2015.
9. C. W. Lu and C. L. Lee, “A low-power high-speed class-AB buffer amplifier for flat-panel-display application,” IEEE Trans. VLSI Syst., vol. 10, pp. 163–168, Apr. 2002.
10. M. C. Weng and J. C. Wu, “A compact low-power rail-to-rail class-B buffer for LCD column driver,” IEICE Trans. Electron., vol. E85-C, no. 8, pp. 1659–1663, Aug. 2002.
11. E. Arslan, M. Yildiz and S. Minaei, “A compact rail-to-rail CMOS buffer amplifier with very low quiescent current,” Int. J. Electron., vol. 102, no. 6, pp. 982–992, 2015.
12. A. D. Grasso, D. Marano, F. Esparza-Alfaro, A. J. Lopez-Martin, G. Palumbo and S. Pennisi, “Self-biased dual-path push-pull output buffer amplifier for LCD column drivers,” IEEE Trans. Circuits Syst. I, vol. 61, no. 3, pp. 663–670, 2014.
13. A. D. Grasso, G. Palumbo and S. Pennisi, “Dual push-pull highspeed rail-to-rail CMOS buffer amplifier for flat-panel displays,” IEEE Trans. Circuits Syst. II, vol. 65, no. 12, pp. 1879–1883, 2018.