EMITTER-COUPLED LOGICINEL4207 - Spring 2014

Figure 15.25 The basic element of ECL is the differential pair. Here, VR is a reference voltage.

R

Q1 Q2

IEE

-VEE

vIN VREF

vC1 Q3

IE3

vO

SIMPLIFIED ECL INVERTER

Example: Select R so that VL = -1.5V. Use IEE = 0.1mA.

R

Q1 Q2

-VEE

vIN VREF

vC1 Q3

IE3

vO

REEIREE

R3

-VEE2

ECL WITH RESISTOR BIASING

Example: Find R and R3 if VEE = VEE2 = −5.2V, VL = −1.3V, IEE = 300μA and IEE2 = 100μA.

R

Q1 Q2

-VEE

vIN VREF

vC1 Q3

IE3

vO

REEIREE

R3

R4

Example: Use the above circuit design an ECL gate for which VH = −1.7V and VL = −2.3V . The average power dissipation should be less that 2mW. The supply voltage is −5.2V . Neglect the base currents.

Figure E15.12

Find VR if vD1 = vD2 = vBE = 0.75V. Neglect iB.

Figure 15.26 Basic circuit of the ECL 10K logic-gate family.

tp ≈ 1ns, the time it takes light to travel 1 foot.

For previous circuit, find IE through RE if A and B are left open. Also find vC,QR and vCA,B. Use VR = -1.32V, VBE=0.75V and a very large β.

Figure 15.27 The proper way to connect high-speed logic gates such as ECL. Properly terminating the transmission line connecting the two gates eliminates the “ringing” that would otherwise corrupt the logic signals. (See Section 15.4.6.)

Figure 15.28 Simplified version of the ECL gate for the purpose of finding transfer characteristics.

Figure 15.28 Simplified version of the ECL gate for the purpose of finding transfer characteristics.

Find VOL and VOH (neglect iC of QR) if β=100. Then find NMH and NML if VIL and VIH are defined as the conditions for which IE, QR/IE, QA = 99 and vice-versa.

Figure 15.30 Circuit for determining VOH.

VOH = -0.88V. Take into account base current and variations in vBE. Assume that at iC = 1mA, vBE = 0.75V.

Figure 15.31 15.28

Figure 15.32

Figure 15.33 Equivalent circuit for determining the temperature coefficient of the reference voltage VR.

δ = -2mV/℃

Figure 15.34 Equivalent circuit for determining the temperature coefficient of VOL

∆VOL = -0.43 δ

Figure 15.35 Equivalent circuit for determining the temperature coefficient of VOH.

∆VOH = -0.93 δ

Figure 15.36 The wired-OR capability of ECL.

Figure P15.30

Figure P15.39

Name: INEL4207 Digital Electronics - A2

Student #: Sec.: December 21, 2010

This exam has 3 problems. Each problem counts for 1/3 of the exam grade.

1. For the ECL inverter shown in the following sketch, the high voltage level is VH = −1.7V andthe average power dissipated when the input is high 50% of the time is P = 5mW . Determinethe source’s current IEE, the low voltage level VL, the reference voltage level VREF and thevalue of resistance R3.

-5.2V-3.3V

VREFvin

2k�

2k�

IEE

Q1 Q2

Q3

voutR3

Name: Student number:

2. Find VL, VH and VREF for the following circuit. Neglect base currents and assumeVBE = 0.7V if a transistor is ON. (25 points)

-2V-5V

1kΩ

1kΩ

VREFvINvOUT

4kΩ

Q1

Q2