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The common-base characteristics I C, I E vs. The shift (≈ 25 mV) is close, as expected, to the GaInAs band gap lowering (≈ 30 meV) as the temperature is varied from 7 to 77 K. Note that at 77 K the peak shifts to a lower voltage. This is expected, since, at a bias ≈ E g + Δ E c/ q ≈ 1.03 V, the conduction band edge in the emitter becomes flat, leading to a steep increase in the injection efficiency. Following this the collector current rises rapidly for V ≥ 1.02 V. In excellent agreement with the experimental value (= 1.00 V). Conduction-band nonparabolicities were included in these envelope function calculations Δ E C = 0.23 eV and Δ E v = 0.39 eV were used for the band discontinuities. Energies are measured from the classical bottom of the conduction and valence band wells, respectively. The calculations show that the ground-state electron miniband extends from 36.6 to 75.2 meV, while the heavy-hole miniband extends from 11.9 meV to 12 meV. This superlattice design ensures the formation of relatively wide minibands, which guarantees Bloch conduction of injected electrons through the base. A 20 Å undoped InP doping set-back layer separates the superlattice from the 5,000 Å-thick n + (≈ 2 × 10 18 cm − 3) InP emitter. The barrier layers are undoped, while all the GaInAs wells are heavily doped (2 × 10 18 cm − 3) p-type. The base consists of a p + (2 × 10 18 cm − 3) Ga 0.47In 0.53As 500 Å-thick region, adjacent to the collector layer, followed by a 20-period Ga 0.47In 0.53As (70 Å)/InP (20 Å) superlattice. The structure is grown by chemical beam epitaxy on an n + 100 InP substrate. Band diagram of superlattice base HBT under injection conditions (a) into the miniband and (b) at the suppression of injection in the miniband.
![transistor base emitter collector voltage transistor base emitter collector voltage](http://i.stack.imgur.com/0Cfhj.png)
9.25Ī 74LS device is connected directly to a 74HC device - is this acceptable?įig. 38. Place in increasing PDP order the following: CMOS TTL ECL BiCMOS. Place in increasing power consumption order the devices in Question 9.21.
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Place in decreasing speed order the following: 74LS 74HC 74ALS 74AC F100K. In CMOS combinational logic what is the relationship between the NMOS transistors and the PMOS transistors? 9.20
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Repeat Question 9.17 for propagation delay. Write down the expression for dynamic power consumption in a CMOS device. 9.16Ī two-input NOR gate has its PMOS transistors in series. 9.15Įxplain why an NMOS device is smaller than an electrically identical PMOS device. Write down the equation for K for a MOS transistor. Why is a Schottky clamped bipolar transistor faster than an unclamped device? 9.13 When would you use the technologies CMOS and TTL? 9.12 What is the difference between 74ACT and 74AC? 9.9įor a TTL device which is the larger: I 1Lmax or I 1Lmax? 9.10 Group into CMOS and TTL the following devices:ħ4ALS 74HC 74 74LS 74AC 74ACT 74F 74HCT 74AHC and 4000B. Place in chronological date order the following: What do the following acronyms stand for: DTL TTL NMOS CMOS ECL BiCMOS? 9.5Ī diode is forward biased if the cathode is more negative than the anode. What base- emitter voltage is needed to turn on a bipolar transistor? 9.3 What is the voltage across a saturated bipolar transistor? 9.2