Activity for Circuit fantasist‭

Type	On...	Excerpt	Status	Date
Article	—	What is the idea behind the transistor differential amplifier? It was a big challenge for me to show the basic idea behind the op-amp instrumentation amplifier by building and reinventing it step by step. But it is no less challenging to show the idea behind the simpler but legendary transistor differential amplifier (figuratively named "long-tailed pair"). I wi... (more)	—	over 1 year ago
Answer	—	A: Find Q point in common base BJT configuration Load line ========= Formal "explanation" > In common emitter collector we just draw a line from the vertical axis (Ic) at the point (0,VCC/RC) to the horizontal axis at the point(VCC,0) and where that line intersects with the IC/VCE curve for some specific IB, there is our operating point… ... (more)	—	almost 2 years ago
Answer	—	A: What reactance actually is? Here is another "functional explanation" of this phenomenon (see also my RG question). General feature. Unlike resistors that directly decrease current, both capacitors and inductors do it by subtracting their voltage from the source voltage creating this current. You can think of them as varyin... (more)	—	about 2 years ago
Article	—	What is the idea behind the op-amp instrumentation amplifier? Building the circuit structure The classic circuit of the op-amp instrumentation amplifier is an example of an ingenious circuit solution. The best way to show it is by reinventing the circuit step by step. Here is my "building scenario"... Step 1: Single-ended amplifier Let's assume the... (more)	—	over 2 years ago
Article	—	Why does the collector current depend linearly on the base current? It is well known that there is a linear relationship between the BJT collector and base current (Ic = beta x Ib). It would be interesting to explain it in an intuitive way. The power of such a "philosophical" approach is that it can explain various specific implementations. The idea In the BJ... (more)	—	over 2 years ago
Article	—	How does a transistor maintain a constant current? In contrast to diodes that maintain a relatively constant voltage when the current through them varies, a fundamental property of all types of transistors (BJT, FET...) is to maintain a relatively constant current when the voltage across them varies. How do they do that? As in the case of diodes, ... (more)	—	over 2 years ago
Article	—	How does a diode maintain a constant voltage? A fundamental property of all types of diodes (silicon, germanium, Schottky, LEDs, Zener ...) is to maintain a relatively constant voltage when the current through them varies. How do they do that? This question can be answered specifically by considering the processes in the semiconductor PN junc... (more)	—	over 2 years ago
Article	—	What are voltages inside resistors? Need to visualize voltage distribution Once visualized the voltages of the internal circuit points, we can go even further and "enter" inside resistors to visualize the voltages along the resistive film. This will allow us to see some interesting points (for example, virtual ground), the operati... (more)	—	over 2 years ago
Article	—	What are voltages in circuits? Need to visualize voltages I hope I have convinced you that a powerful technique for explaining circuits in an intuitive way is to show where currents flow. But since currents are created by voltages, it is even more important to show what voltages of the internal circuit points are. Voltages... (more)	—	over 2 years ago
Article	—	Where do currents flow in circuits? Need to visualize currents I have long understood that one of the most important techniques to understand circuits is to see where currents flow inside them (in circuit theory, this is considered unimportant and, at best, currents are represented by small arrows with arbitrary direction). The... (more)	—	over 2 years ago
Answer	—	A: Change of pins in monostable multivibrator Your circuit will make sense if you do two things: significantly increase both R3 and R4 reverse D1 or move it to Q1's base Let's first see the role of the resistances R3 and R4. These are base resistors; so their resistances should be higher than the collector resistances R1 and R2. F... (more)	—	over 2 years ago
Answer	—	A: Help with differential to single ended voltage converter My Comment ========== I will begin my answer by commenting on the other two answers from two months ago. I will show that they do not contradict but rather complement each other. Ideal current sources. I can not agree with Olin Lathrop's assertion that this arrangement "works fine for ideal cu... (more)	—	over 2 years ago
Answer	—	A: Is it possible for one transistor to switch between two loads? When, two months ago, I accidentally found out about the new Codidact platform, I was happy and decided to take part in it. I wanted to mark this event with an interesting question that would arouse the interest of visitors to the new platform. Thus I remembered an interesting inventive idea from the... (more)	—	over 3 years ago
Question	—	I can not upload pictures I can not upload pictures when I start a new answer to a question (I have no problem when I edit an old answer). When I click the "insert picture" button, nothing happens and I do not see the window: The window about inserting a picture Here are the messages in the console: Console Final ... (more)	—	over 3 years ago
Answer	—	A: How to plot the I-V curve of a tunnel diode? Setup We can best understand the behavior of the tunnel diode in the region with negative resistance if we imagine it as a self-variable (dynamic) resistor R driven by a variable voltage source V - Fig. 1. If OP has a subtle sense of humor, I suggest we conduct this experiment in the form of a f... (more)	—	over 3 years ago
Answer	—	A: What is the difference between differential amplifier and differentiator? Both differential amplifier and differentiator react to a voltage difference. But in the differential amplifier, the difference is between two voltages applied to the amp inputs at the same time while in the differentiator, the difference is between two voltage values at adjacent moments of time. ... (more)	—	over 3 years ago
Article	—	How to create current sources Background Constant current sources (simply, current sources) are useful and necessary devices. They are widely used to drive LEDs, charge capacitors and batteries, bias differential amplifiers, etc. The only problem is that... there are no such devices in nature; almost all of sources are (cons... (more)	—	over 3 years ago
Answer	—	A: Using FET based followers and design rules > ... it is still unclear to me how to determine the voltage drop introduced by these transistors... Very interesting question... I have asked myself many times in the past... and I have not been able to answer it... but now I think I have already succeeded... Maybe Codidact acts as a kind of "cat... (more)	—	over 3 years ago
Article	—	3-LED voltage indicator (an inventor's story) Goals and objectives Motivation. Having shown how a 1-transistor circuit can be invented, now I will demonstrate how we can invent another more complex 2-transistor circuit. As before, my goals are two - specific (the very 2-transistor circuit) and general (the technology of invention). With my ... (more)	—	over 3 years ago
Answer	—	A: ESD Protection - Differential Amplifier Although the voltage drop across the current-sensing resistor R6 is floating and it can "move" between the 28 V rails, the A1A op-amp input voltages can (have to) vary within the 5 V power supply. So, you can protect the op-amp (and the whole circuit) against any overvoltages by connecting a bidir... (more)	—	over 3 years ago
Article	—	Battery backup voltage regulator (an invention story) Goals and objectives Motivation. Inspired that there is a place on the web where simple but clever circuit ideas are encouraged, I decided to share another 1-transistor circuit trick. Besides, to make the story even more interesting than before, I decided to show, step-by-step, how the circuit w... (more)	—	over 3 years ago
Answer	—	A: De-bouncing input signals? Another hardware solution There is another hardware debouncing technique widely used in the past. It is implemented by an SPDT push button driving (buffered by) an RS latch. SR debouncer (ganssle.com) This configuration can be thought of as an "electromechanical timer 555" since it is b... (more)	—	over 3 years ago
Article	—	Charge amplifier (a qualitative view) Goals and objectives As can be seen from the name of the new platform (Codidact = Co + didact), it claims to use the principles of didactics (the art and science of teaching) for the purposes of the Electrical Engineering section as well. And since I have been involved in didactics in electronic... (more)	—	over 3 years ago
Answer	—	A: Why Ib=const. for BJT output characteristics Ic=f(Vce) I fully agree with OP considerations about measuring the transistor output curve. We can very easily and precisely set successive current values with constant increment. Thus, the IV curves will be evenly spaced vertically (equidistant from each other). Let me generalize these observations into a ... (more)	—	over 3 years ago
Answer	—	A: How to calculate pullup resistor value for pushbutton? Figuratively speaking, Olin Lathrop's answer is a wonderful story about the unequal "tug of war" between a "pulling up" resistor and "pulling down" switch. And, when the switch is 'off', the "struggle" is between the resistor and input leakages… and then the resistor must win. To be more precise, ... (more)	—	over 3 years ago
Question	—	Can I ask a question to which I have a possible answer? For many years I have been working on unraveling the basic ideas behind famous circuit solutions. Thus I gradually managed to accumulate a collection of circuit principles and clever tricks. I have my intuitive explanations of circuit phenomena that significantly differ from classic formal explanatio... (more)	—	over 3 years ago
Question	—	Is it possible for one transistor to switch between two loads? The output collector-emitter part of a transistor can be thought of as a 2-terminal SPST switch controlled by the input base-emitter voltage or base current. So this transistor switch can control only a single collector load. Is it possible to make the transistor act as a 3-terminal SPDT switch? I... (more)	—	over 3 years ago
Answer	—	A: Purpose of emitter resistor in a common collector amplifier In addition to the previous considerations, I will add a few more. Stages with voltage output (such as a voltage follower) are implemented as voltage dividers consisting of two elements in series "stretched" between supply rails. One of them is "pulling up" and the other is "pulling down" the comm... (more)	—	over 3 years ago
Answer	—	A: Emitter Bypass Capacitor in a CE Amplifier With the capacitor C3 disconnected, the stage has a minimum gain and with C3 connected it has a maximum gain. There is a compromise solution with a moderate gain - to connect a resistor in series to C3. (more)	—	over 3 years ago