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| university:courses:alm1k:alm-lab-13a [27 Jan 2021 22:35] – use wp> interwiki links Robin Getz | university:courses:alm1k:alm-lab-13a [06 Sep 2021 16:20] – [Another Configuration:] Doug Mercer |
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| =====Another Configuration:===== | =====Another Configuration:===== |
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| Remembering the loop formed by the base emitter voltages of Q<sub>1</sub>, Q<sub>2</sub>, Q<sub>3</sub> and Q<sub>4</sub> we also know that the order of the voltage drops around the loop can be interchanged. So if we interchange the V<sub>BE</sub>'s of NPN Q<sub>1</sub> and PNP Q<sub>3</sub> we get the configuration shown in figure 3. Some of you may recognize the combination of Q<sub>3</sub> and Q<sub>2</sub> as the low offset follower we discussed earlier in the lab section on emitter followers. The circuit uses the V<sub>BE</sub> shift up of a PNP emitter follower to partially cancel the V<sub>BE</sub> shift down of an NPN emitter follower. Transistors Q<sub>1</sub> and Q<sub>4</sub>are simply the complement of Q<sub>3</sub> and Q<sub>2</sub>. | Remembering the loop formed by the base emitter voltages of Q<sub>1</sub>, Q<sub>2</sub>, Q<sub>3</sub> and Q<sub>4</sub> we also know that the order of the voltage drops around the loop can be interchanged. So if we interchange the V<sub>BE</sub>'s of NPN Q<sub>1</sub> and PNP Q<sub>3</sub> we get the configuration shown in figure 3. This arrangement is sometime referred to as a "diamond buffer" because of the shape formed by the four emitter / base connections. Some of you may recognize the combination of Q<sub>3</sub> and Q<sub>2</sub> as the low offset follower we discussed earlier in the lab section on emitter followers. The circuit uses the V<sub>BE</sub> shift up of a PNP emitter follower to partially cancel the V<sub>BE</sub> shift down of an NPN emitter follower. Transistors Q<sub>1</sub> and Q<sub>4</sub> are simply the complement of Q<sub>3</sub> and Q<sub>2</sub>. |
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