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Class Exercise 6 (April 12 - 17, 2004)

6. Transistor Circuits without Feedback

So far, we have managed to derive, build and even "invent" a total of 46 circuit building blocks. All these devices are not able to inject energy into the circuits. Now, we will enrich our library with a further 6 building blocks; so, it will grow to 52 basic circuits:

6.1. Functional notion of "amplification" . Discussions: Is it possible to amplify energy? What does an amplifier really do? Block diagrams: series and parallel connection (advantages and disadvantages). Functions of the constituent parts. Characteristic curve of an ideal "amplifying" element.

6.2. Bipolar transistor as an "amplifying" element (grounded-emitter stage). Functional notion of the input base-emitter part (RV non-linear element), of the output collector-emitter part (electrical controlled RI non-linear element) and of the direct input-output connection (current-to-current converter).
6.2.1. Circuits with series connected transistor to the load. Versions: amplifier with grounded transistor and "flying" load; amplifier with "flying" transistor and grounded load. Discussions: What is the big problem of the series circuit in relation to the common ground? Is the circuit inverting? Does the load influence the circuit operation and how?
6.2.2. Circuits with parallel connected transistor to the load. Solving the problem of the common ground. Circuit versions. Discussion: Is the circuit inverting? How does the load influence the circuit operation?
6.2.3. Applications: transistor switch (assembling from more elementary voltage-to-current; current-to-current and current-to-voltage converters. Discussion: What kind of analog device is the transistor switch - digital or analog? Do digital elements really exist?

6.3. FET transistor as an "amplifying" element (grounded-source stage). Functional notion of the input gate-source part (-), of the output drain-source part (electrically controlled RI non-linear element) and of the direct input-output connection (voltage-to-current converter).
6.3.1. Circuits with series connected transistor to the load - as 6.2.1.
6.3.2. Circuits with parallel connected transistor to the load - as 6.2.2.
6.3.3. Applications: FET transistor switch (assembling from more elementary voltage-to-current and current-to-voltage converters.

6.4. Biasing circuits. Functional notion of the "bias" idea (necessity). Presenting the biasing using the operation of summing and scaling.
6.4.1. Dynamic biasing - "shifting" potential variations by blocking capacitors. Applications: an ac amplifier (the input and the output part). Visualizing theoperation using potential bars.
Coupling Circuits & Techniques

6.4.2. Static biasing. Applications: diode "shifting" circuits in transistor push-pull amplifiers; resistive "shifting" circuits in the op-amp circuits, ADCs and DACs. Visualizing the operation using potential bars.

6.5. Transistor as a current-stable non-linear element.
6.5.1. Functional notion of the RI non-linear element. Characteristic curves of an ideal RI element. The output collector-emitter part as a current-stable element. Simplified IV characteristic curve.
6.5.2. Constant current source. Discussion 1: How do we make a constant current source (possible ways)? How did we make very good and even an ideal current source in electricity (remember method 1? What are its imperfections? How do we overcome them by using electronic components? Remedy: Keeping constant the overall circuit resistance by changing the current internal source resistance (method 2). Discussion 2: Is it a circuit with feedback? May we imagine that it is? What is the benefit of this notion?

6.5.3. Transistor constant current source/sink. Applications in analog circuitry: building a transistor amplifier from electrically controlled current source and current-to-voltage converter; dynamic load in differential amplifiers; ramp generator - building the circuit by means of transistor current source and C integrator. Discussion: Is the transistor current source in the circuit of a ramp generator a common-base or a common-collector stage (revealing a misconception)?

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