M niknejad and b boser 9 temperature coefficient tc

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Unformatted text preview: -biasing Temperature Coefficient Vertical BJT Startup © 2006 A. M. Niknejad and B. Boser 9 Temperature Coefficient TC of Reference Voltage: TCF = = 1 d∆VBE ∆VBE dT 1 ∆VBE ∆VBE T 1 T ≅ 3300ppm/K at room temperature (300o K ) = TC of Reference Current: I out = TCF = = ∆VBE R1 1 dI out I out dT 1 d∆VBE 1 dR1 − R1 dT ∆VBE dT = 3300ppm/K − 1500ppm/K = 1800ppm/K for n + diffusion resistor EECS 240 Lecture 8: References © 2006 A. M. Niknejad and B. Boser 10 CMOS PTAT Reference Vertical PNP p- substrate p+ diffusion n- well n+ diffusion C E B EECS 240 Lecture 8: References © 2006 A. M. Niknejad and B. Boser 11 Startup Circuit IQ2 Widlar Source B Mirror A IQ1 Parasitic operating point A: • Positive feedback unstable • Noise drives circuit away from A (and to B) • Problem: gain at A too small (IQ = 0) EECS 240 Lecture 8: References © 2006 A. M. Niknejad and B. Boser 12 Bandgap Reference • • • • Supply and temperature insensitive VBG,Si = 1.205V Curvature correction References: – R. Widlar, JSSC 2/1971, pp. 2 first report – G. Nicollini, JSSC 1/1991, pp. 41 offset compensated amplifier – K. Tham, JSSC 5/1995, pp. 586 self-regulated supply for improved PSRR – A. Boni, JSSC 10/2002, pp. 1339 bandgap reference for VDD < VBG – P. Malcov...
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This note was uploaded on 03/18/2014 for the course EECS 240 taught by Professor Boser during the Spring '04 term at University of California, Berkeley.

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