Analog Education

2-wire analog outputs with precision DACs

3-wire analog outputs with precision DACs

Capacitors store energy in the form of an electric field, and electrically manifest that stored energy as a potential: static voltage. Inductors store energy in the form of a magnetic field, and electrically manifest that stored energy as a kinetic motion of electrons: current. Capacitors and inductors are flip-sides of the same reactive coin, storing and releasing energy in complementary modes. When these two types of reactive components are directly

While the C-B (common-base) amplifier is known for wider bandwidth than the C-E (common-emitter) configuration, the low input impedance (10s of Ω) of C-B is a limitation for many applications. The solution is to precede the C-B stage by a low gain C-E stage which has moderately high input impedance (kΩs). See Figure below. The stages are in a cascode configuration, stacked in series, as opposed to cascaded for a

Our next transistor configuration to study is a bit simpler for gain calculations. Called the common-collector configuration, its schematic diagram is shown in Figure below. Common collector amplifier has collector common to both input and output. It is called the common-collector configuration because (ignoring the power supply battery) both the signal source and the load share the collector lead as a common connection point as in Figure below. Common collector:

Don’t just sit there! Build something!! Learning to mathematically analyze circuits requires much study and practice. Typically, students practice by working through lots of sample problems and checking their answers against those provided by the textbook or the instructor. While this is good, there is a much better way. You will learn much more by actually building and analyzing real circuits, letting your test equipment provide the “answers” instead

The goal of series-parallel resistor circuit analysis is to be able to determine all voltage drops, currents, and power dissipations in a circuit. The general strategy to accomplish this goal is as follows: Step 1: Assess which resistors in a circuit are connected together in simple series or simple parallel. Step 2: Re-draw the circuit, replacing each of those series or parallel resistor combinations identified in step 1 with a single, equivalent-value resistor.

PARTS AND MATERIALS Low-voltage AC power supply (6-volt output) Two 1N4001 rectifying diodes (Radio Shack catalog # 276-1101) Small “hobby” motor, permanent-magnet type (Radio Shack catalog # 273-223 or equivalent) Audio detector with headphones 0.1 µF capacitor One toggle switch, SPST (“Single-Pole, Single-Throw”) It is essential for this experiment that the low-voltage AC power supply is equipped with a center tap. A transformer with a non-tapped secondary winding simply will not work for

Schottky diodes Schottky diodes are constructed of a metal-to-N junction rather than a P-N semiconductor junction. Also known as hot-carrier diodes, Schottky diodes are characterized by fast switching times (low reverse-recovery time), low forward voltage drop (typically 0.25 to 0.4 volts for a metal-silicon junction), and low junction capacitance. The schematic symbol for a Schottky diode is shown in Figure below. Schottky diode schematic symbol. The forward voltage drop (VF), reverse-recovery time

The single-transistor inverter circuit illustrated earlier is actually too crude to be of practical use as a gate. Real inverter circuits contain more than one transistor to maximize voltage gain (so as to ensure that the final output transistor is either in full cutoff or full saturation), and other components designed to reduce the chance of accidental damage. Shown here is a schematic diagram for a real inverter circuit, complete

In instrumentation circuitry, DC signals are often used as analog representations of physical measurements such as temperature, pressure, flow, weight, and motion. Most commonly, DC current signals are used in preference to DC voltage signals, because current signals are exactly equal in magnitude throughout the series circuit loop carrying current from the source (measuring device) to the load (indicator, recorder, or controller), whereas voltage signals in a parallel circuit may

We finished our discussion of transformer circuits in our last lesson when we were looking at the Zs. We came up with this formula that said the Zp=(Np/Ns)2*Zs. We're going to apply that in a circuit in just a moment but before we do that, I just want to mention a little bit about what is impedance. Impedance is … when we talk about resistance, impedance is a

In this circuit, three resistors receive the same amount of voltage (24 volts) from a single source. Calculate the amount of current “drawn” by each resistor, as well as the amount of power dissipated by each resistor:

Suppose we were to wrap a coil of insulated wire around a loop of ferromagnetic material and energize this coil with an AC voltage source: (Figure below (a)) Insulated winding on ferromagnetic loop has inductive reactance, limiting AC current. As an inductor, we would expect this iron-core coil to oppose the applied voltage with its inductive reactance, limiting current through the coil as predicted by the equations XL = 2πfL and

PARTS AND MATERIALS Two 6 volt batteries One capacitor, 0.1 µF, non-polarized (Radio Shack catalog # 272-135) One 555 timer IC (Radio Shack catalog # 276-1723) Two light-emitting diodes (Radio Shack catalog # 276-026 or equivalent) One 1 MΩ resistor One 100 kΩ resistor Two 510 Ω resistors Audio detector with headphones Oscilloscope (recommended, but not necessary) An oscilloscope would be useful in analyzing the waveforms produced by this circuit, but it is not essential. An audio detector is a

As we’ve seen, negative feedback is an incredibly useful principle when applied to operational amplifiers. It is what allows us to create all these practical circuits, being able to precisely set gains, rates, and other significant parameters with just a few changes of resistor values. Negative feedback makes all these circuits stable and self-correcting. The basic principle of negative feedback is that the output tends to drive in a

A calculator for computing the gain and output voltage of an operational amplifier

A similar effect happens in series inductive/capacitive circuits. (Figure below) When a state of resonance is reached (capacitive and inductive reactances equal), the two impedances cancel each other out and the total impedance drops to zero! Simple series resonant circuit. With the total series impedance equal to 0 Ω at the resonant frequency of 159.155 Hz, the result is a short circuit across the AC power source at resonance. In the circuit

Now we come to the most popular application of the diode: rectification. Simply defined, rectification is the conversion of alternating current (AC) to direct current (DC). This involves a device that only allows one-way flow of electrons. As we have seen, this is exactly what a semiconductor diode does. The simplest kind of rectifier circuit is the half-wave rectifier. It only allows one half of an AC waveform to pass

The interlock contacts installed in the previous section’s motor control circuit work fine, but the motor will run only as long as each push button switch is held down. If we wanted to keep the motor running even after the operator takes his or her hand off the control switch(es), we could change the circuit in a couple of different ways: we could replace the push button switches

Value of time constant in series RC and RL circuits Time constant in seconds = RC Time constant in seconds = L/R Calculating voltage or current at specified time Calculating time at specified voltage or current

Since transformers are essentially AC devices, we need to be aware of the phase relationships between the primary and secondary circuits. Using our SPICE example from before, we can plot the waveshapes (Figure below) for the primary and secondary circuits and see the phase relations for ourselves: spice transient analysis file for use with nutmeg: transformer v1 1 0 sin(0 15 60 0 0) rbogus1 1 2 1e-12 v2 5 0 dc 250 l1 2 0 10000 l2 3 5 100 k l1 l2 0.999 vi1 3 4 ac 0 rload 4 5