Cryogenic 0.35 μ m CMOS Technology RESULTS AND MODEL VALIDATION Figure 8 shows the output voltage reference circuit obtained by simulation and measurements respectively. The circuit is powered with a 5.5 V supply. The measured voltage curves fit quite well with the simulation one. Furthermore, the circuit shows a low drift regarding to power supply variations: less than 3 mV for 1 V power supply sweep over the whole temperature range. Table 3 summarizes circuit performances giving the reference voltage drift and its equivalent thermal drift with 1.6 gain amplification. Over fifty degrees range, from 100 K to 150 K, the voltage drifts is about 1 mV corresponding to a 20 ppm/K drift. The volt- Figure 7. Table 3. Full CMOS bandgap reference circuit schematic. Figure 7 presents the full CMOS bandgap schematic. The two PTAT components are the resistance R and the diode transistor M12. They have to be properly design in order to cancel out their voltage variations. The M8 transistor is used like a start-up circuit [14]. Table 2 specifies the circuit components dimensions. Transistors sizes are within the dimensions presented previously for the extracted model to remain valid. The bandgap output provides a voltage reference about 0.8 V, depending on the foundry process. An amplifier having a 1.6 voltage gain (not shown) is added as a buffer to achieve the desired voltage reference of 1.3 V. Voltage Reference Variation with Temperature ΔV (mV) Gain Amp. × 1.6 (Buffer Amp.) Thermal Drift (ppm/°K) [90; 300] 85 (56) 425 (280) [90; 190] 7 (5) 70 (50) [100; 150] 1 (<1) 20 (14) ΔT (°K) NOTE: The values under brackets correspond to the bandgap output, measured with an amplifier buffer. Table 2. Bandgap Circuits Components Values of Figure 7 Design Name Type W/L M1 PMOS 50 μm/500 μm M2 PMOS 150 μm/40 μm M3 PMOS 150 μm/40 μm M4 PMOS 150 μm/40 μm M5 PMOS 150 μm/40 μm M6 PMOS 400 μm/200 μm M7 NMOS 100 μm/5 μm M8 NMOS 50 μm/5 μm M9 NMOS 50 μm/40 μm M10 NMOS 50 μm/40 μm M11 NMOS 50 μm/40 μm M12 NMOS 600 μm/40 μm R1 Resistor 28 Figure 8. Simulation and measurements of the voltage reference circuit with respect to the temperature. 5kΩ IEEE A&E SYSTEMS MAGAZINE AUGUST 2018