Datasheet LT1671 (Analog Devices) - 9
| Fabricante | Analog Devices |
| Descripción | 60ns, Low Power, Single Supply, Ground-Sensing Comparator |
| Páginas / Página | 12 / 9 — APPLICATIONS INFORMATION. Figure 3. Simplified LT1671 Output Stage. … |
| Formato / tamaño de archivo | PDF / 214 Kb |
| Idioma del documento | Inglés |
APPLICATIONS INFORMATION. Figure 3. Simplified LT1671 Output Stage. Figure 4. Level Shift Has Noninverting Voltage Gain
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LT1671
U U W U APPLICATIONS INFORMATION
+V LT1671 is the key to low delay, providing Q2’s base with nearly ideal drive. This capacitor loads the LT1671’s output transition, but Q2’s switching is clean with 3ns OUTPUT = 0 → +V (TYPICALLY 3V TO 4V) delay on the rise and fall of the pulse. Figure 6 is similar to Figure 4 except that a sink transistor has replaced the Schottky diode. The two emitter-followers drive a power MOSFET that switches 1A at 15V. Most of the 7ns to 9ns 1671 F03 delay in this stage occurs in the MOSFET and the 2N2369.
Figure 3. Simplified LT1671 Output Stage
When designing level shifters, remember to use transis- tors with fast switching times and high fT. To get the kind 15V of results shown, switching times in the nanosecond 1k range and an fT approaching 1GHz are required. 2N2369 + 2N3866 LT1671 HP5082-2810 15V OUT – 1k 12pF 1k 1k R 2N2369 L 1671 F04 RISE TIME = 4ns + 2N3866 FALL TIME = 5ns POWER LT1671 FET
Figure 4. Level Shift Has Noninverting Voltage Gain
– 2N5160 1k 1k 12pF Figure 5 is a very versatile stage. It features a bipolar swing 1671 F06 RISE TIME = 7ns that is set by the output transistor’s supplies. This 3ns FALL TIME = 9ns delay stage is ideal for driving FET switch gates. Q1, a gated current source, switches the Baker-clamped output
Figure 6. Noninverting Voltage Gain Level Shift
transistor, Q2. The heavy feedforward capacitor from the 5V + INPUT LT1671 4.7k 430Ω 1N4148 – 5V (TYP) Q1 2N2907 1000pF 0.1µF 820Ω 330Ω HP5082-2810 5V OUTPUT TRANSISTOR SUPPLIES (SHOWN IN HEAVY LINES) OUTPUT CAN BE REFERENCED ANYWHERE –10V BETWEEN 15V AND –15V Q2 2N2369 1671 F05 RISE TIME = 3ns 820Ω FALL TIME = 3ns –10V (TYP)
Figure 5. Level Shift with Inverting Voltage Gain—Bipolar Swing
9
U U W U APPLICATIONS INFORMATION
+V LT1671 is the key to low delay, providing Q2’s base with nearly ideal drive. This capacitor loads the LT1671’s output transition, but Q2’s switching is clean with 3ns OUTPUT = 0 → +V (TYPICALLY 3V TO 4V) delay on the rise and fall of the pulse. Figure 6 is similar to Figure 4 except that a sink transistor has replaced the Schottky diode. The two emitter-followers drive a power MOSFET that switches 1A at 15V. Most of the 7ns to 9ns 1671 F03 delay in this stage occurs in the MOSFET and the 2N2369.
Figure 3. Simplified LT1671 Output Stage
When designing level shifters, remember to use transis- tors with fast switching times and high fT. To get the kind 15V of results shown, switching times in the nanosecond 1k range and an fT approaching 1GHz are required. 2N2369 + 2N3866 LT1671 HP5082-2810 15V OUT – 1k 12pF 1k 1k R 2N2369 L 1671 F04 RISE TIME = 4ns + 2N3866 FALL TIME = 5ns POWER LT1671 FET
Figure 4. Level Shift Has Noninverting Voltage Gain
– 2N5160 1k 1k 12pF Figure 5 is a very versatile stage. It features a bipolar swing 1671 F06 RISE TIME = 7ns that is set by the output transistor’s supplies. This 3ns FALL TIME = 9ns delay stage is ideal for driving FET switch gates. Q1, a gated current source, switches the Baker-clamped output
Figure 6. Noninverting Voltage Gain Level Shift
transistor, Q2. The heavy feedforward capacitor from the 5V + INPUT LT1671 4.7k 430Ω 1N4148 – 5V (TYP) Q1 2N2907 1000pF 0.1µF 820Ω 330Ω HP5082-2810 5V OUTPUT TRANSISTOR SUPPLIES (SHOWN IN HEAVY LINES) OUTPUT CAN BE REFERENCED ANYWHERE –10V BETWEEN 15V AND –15V Q2 2N2369 1671 F05 RISE TIME = 3ns 820Ω FALL TIME = 3ns –10V (TYP)
Figure 5. Level Shift with Inverting Voltage Gain—Bipolar Swing
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