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.

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]

Simple Telephone Ring Tone Generator Circuit

This is the figure simple telephone ring tone generator circuit designed using only a few components. It produces simulated telephone ring tone and needs only DC voltage (4.5V DC to 12V DC). One may use this circuit in ordinary intercom or phone-type intercom. This is the figure of the circuit;

The sound is quite loud when this circuit is operated on +12V DC power supply. However, the volume of ring sound is adjustable. The commonly available 14-stage binary ripple counter with built-in oscillator (CMOS IC CD4060B) is used to generate three types of pulses, which are available from pin 1 (O11), pin 3 (O13), and pin 14 (O7), respectively. Preset VR1 is adjusted to obtain 0.3125Hz pulses (1.6- second ‘low’ followed by 1.6-second ‘high’) at pin 3 of IC1. At the same time, pulses available from pin 1 will be of 1.25 Hz (0.4-second ‘low’, 0.4-second ‘high’) and 20 Hz at pin 14. The three output pins of IC1 are connected to base terminals of transistors T1, T2, and T3 through resistors R1, R2, and R3, respectively.

Simple Generator 9 V DC Unregulated Circuit

This is a design circuit to generate the -9V supply that is used by the row drivers as the off voltage for the TFT gate. This circuit is very simple design using LM2622. The LM2622 can be used in conjunction with a diode inverter circuit. This is the figure of the circuit;

The diode inverter works in the following manner. When the switch of the LM2622 is open, D4 conducts and the voltage across C7 charges to approximately +9.0V. When the switch closes, the voltage on the SW pin is suddenly dropped to GND. Because the voltage across C7 cannot change instantaneously, the voltage between D4 and D5 is −9.0V when referenced to GND. In general, this configuration will generate an unregulated voltage that is equal in magnitude but opposite in sign to the regulated supply.

[Circuit source: National Semiconductor Notes]

Simple Micro Power Pulse Generator

This is a simple design for pulse generator. This circuit is based on op amp. This is the figure of the circuit.


This circuit produces clean logic pulses while drawing very low current. This circuit is designed to produce short 2mS pulses at a rate of one per second while drawing only 1 micro amplifier from a 9 volt battery.

Simple Saw Tooth Wave Generator Circuit Using NE555 IC

This is a simple design circuit for generating a saw tooth wave form using a NE555 IC. The frequency of the wave form can be varied by using a POT. This is the figure of the circuit.


The operation of the circuit is if the capacitor C, resistor R and zener diode forms a constant current source for charging of the capacitor. When the voltage across capacitor reaches 2/3 Vcc the internal comparator inside 555 goes on and capacitor discharges. When the voltage across the capacitor goes below 1/3 Vcc the internal comparator goes off and now capacitor starts charging. As a result the capacitor will be switched between 2/3 Vcc and 1/3 Vcc, resulting in a saw tooth wave form across the capacitor. The diode make the output voltage to zero during the discharge phase. The frequency of the output voltage can be given by the equation,

f = (Vcc-2.7)/(R*C*Vpp).

Where Vcc is the supply voltage and Vpp is the peak voltage of the output required.