Simple Shunt Series Pair Wideband Amplifier Circuit

This is a circuit for a Shunt Series Pair Wideband Amplifier circuit. This circuit has four feedback loops, they are two emitters feedback, shunt-shunt feedback and an AC feedback loop(series-shunt). This is a very stable circuit and can be used for wideband amplifiers and low gain. This circuit requires +12 supply that restrict the “headroom” of the second resistor. The emitter of the second transistor feed the a shunt-shunt feedback resistor whose upper end that can give more current without causing a grater voltage drop in the collector resistor. This is the figure of the circuit;

Beside shunt-shunt feedback, this circuit has an AC feedback loop(series-shunt). The DC bias is blocked by 0.1uF capacitor. The amplifier has gain of about 12 if AC feedback loop is removed. AC feedback loop’s gain is 2.8, so this circuit has gain of 3.16. At 1Khz, the gain of this circuit is 3.11. Be careful large loop gains are dangerous at high frequencies.

Simple Peak Detector Circuit

This is a circuit that had detects the peak voltage of the input waveform Vin and outputs it as Vout. This is the figure of the circuit;

The circuit uses a dual operational amplifier IC, the 1458, which is a single IC package that houses two individual op-amps.  In this circuit, the first op-amp is used as a voltage follower whose output is used to charge the capacitor C1 through D1.  As such, the voltage to which capacitor C1 charges up to is the maximum voltage that the input waveform reached, i.e., its peak voltage. 

  

The second op-amp of the 1458 is used as a buffer that outputs the capacitor voltage with negligible loss in the capacitor charge.  The reset switch is used to discharge the capacitor if a new input peak voltage needs to be detected. 

Simple Passive Treble Control for Guitar Pedal

The R1/C1 network makes a low pass filter when the wiper is at the grounded end of the tone pot, and there is a treble cut. The C1 cap bypasses R2 when the wiper is adjusted so that it is at the top end of the pot and it creates a treble boost. This is the figure of the diagram;

The 100k output volume and the 100k tone pot are always in parallel as a constant load. It’s suggested to used a linear taper pot for the tone control and a log (audio) taper for the volume control. Suggested values for initial experimentation are R1=10k, R2=47k, and C1=0.022uF. Some signal loss, as with any passive network is the limitation of this combined tone control. However, many guitar pedal designs have strong enough output signal level, and this tone control is an excellent option for those circuits with enough drive.

Simple LM2576 Switching Regulator

This is a circuit that can be used to produce any output voltage, an external feedback resistors can be added. The sLM2576 is a Switching Regulator that can produce 15, 12, 5, 0r 3.3V output voltage from maximum supply voltage of 60V or 40V. This LM2476 featured with voltage reference, switch and feedback path for use in either the negative boost or the buck saturation voltage of The LM2576 switch is typically 1.4V. A heat sink may be needed to solve the power dissipation, however the thermal dissipation is internally limited. The LM2576 has quiescent current of 50 µA in standby (on/off high). This circuit is a testing circuit for LM276. This is the figure of the circuit;

The electrolytic capacitors at output and input should be connected with leads as close as possible. The power dissipation must be small because the load is 100R, so the heat sink is not needed. The capacitor’s voltage must higher than the voltages used in the experiment. This circuit uses 40V, 1A Schottky diode or the 40V, 3A 1N5822 for heavier currents.

SIDAC Basic Operation

Silicon Diode for Alternating Current, SIDAC, is a multilayer silicon semiconductor switch. This component is triggered by voltage and can be operated as bidirectional switch. Usually, this SIDAC is used in cheap high voltage power supply or ignition circuits. This is the figure shows SIDAC block construction, schematic symbol and geometric construction:

The SIDAC has leakage current(Idrm) less than 5 µA during off state. When the SIDAC receive a supply voltage greater than SIDAC Vbo, the device will turn to a negative resistance switching mode with characteristic like an avalanche diode. The SIDAC will turn on when it supplied with enough current(Is), it allows high current to flow. The magnitude of the current flow affect the voltage drop when the voltage accross the SIDAC. The SIDAC is still on as long as holding current is less than maximum value(150mA). The switching current (Is) is very near the holding current (Ih). A discharging small capacitor can generate current of 10A to 100A to primary or small, very high-voltage transformers for 10 µs to 20 µs when the SIDAC switches.

555 IC Linear Ramp (Sawtooth) Generator/Oscillator Circuit

The Vc1 increases linearly when the pull-up resistor RA in the mono stable circuit is replaced with constant current source, generating a linear ramp. This is the figure that shown the linear ramp generating circuit and the generated linear ramp waveforms illustration;

Current source is created by PNP transistor Q1 and resistor R1, R2, and Re.

Ic= (Vcc-Ve)/Re

Ve= Vbe + (R2/(R1+R2))Vcc

For example, if Vcc=15V, RE=20k, R1=5kW, R2=10k, and VBE=0.7V, VE=0.7V+10V=10.7V, Ic=(15-10.7)/20k=0.215mA

The current flowing through capacitor C1 becomes a constant current generated by PNP transistor and resistor when the trigger starts in a timer configured as shown in figure below.

Hence, the Vc is linear function. The gradient S of the linear ramp function is defined as:

S= (Vp-p)/T

The Vp-p is the peak to peak voltage. The Vc comes out as follows is the electric charge amount accumulated in the capacitor is divided by the capacitance.

V= Q/C

The above equation divided on both sides by T gives us

V/T= (Q/T)/C

and may be simplified into the following equation.

S=I/C

In other words, we can obtained the gradient of the linear ramp function appearing across the capacitor by using the constant current flowing through the capacitor. The gradient of the ramp function at both ends of the capacitor is S = 0.215m/0.022? = 9.77V/ms if the constant current flow through the capacitor is 0.215mA and the capacitance is 0.02uF. [Circuit's schematic diagram source: Philips Semiconductors Application Notes]