Simple Single Pole Active Filter Circuit

This circuit is a design circuit for tool calculated the required resistor and capacitor values for a single pole active filter. The routine assumes the input signal swing will be differential peak swing of 80%*VDD. Given the SNR, and the swing the resistor and capacitors can be sized. This is a simple form circuit.

This is the figure of the circuit;


Part and characteristic;

Inputs
Voltage Gain V/V
3dB bandwidth Hz
Signal to Noise Ratio dB
Supply Voltage V

Outputs
R1 kΩ
Rf kΩ
Cf pf

Simple LED Light Flasher Circuit

This is a simple LED flasher project that uses a CMOS 74C04 Integrated Circuit to alternately ON and OFF two LEDs that are connected in parallel. The Hex inverter MM74C04 from Fairchild Semiconductor has a wide operating power supply voltage range from 3V to 15V DC. This is the figure of the circuit;


It has a typical low power consumption of 10nW/package and has high noise immunity. It is back to back compatible with the standard 74 logic family which is freely available in the market. All its inputs have diode clamps to VCC and GND which protect them from damage due to electrostatic discharge. The schematic above shows the simple configuration of the project. It uses two inverters U1A and U1B to form an oscillator configuration where the frequency of the oscillation is given by :

f = 1/[1.4RC]
= 1/[1.4(10 M Ohm)(0.1uF)]
= 0.7 Hz

The square wave frequency of 0.7 Hz is used to feed the input of U1D which is used as a buffer circuit. At the same time, the other inverter U1C gets its input from pins 2 and 3 of U1. With this configuration, when U1D output is high, U1C output will be low and vice versa. In this way when LED1 is ON, LED2 will be OFF and this will alternate at a frequency of 0.7Hz.
The current that goes through the LED is given by:

I = (9V-7V)/510 ohm
= 14mA

It is assumed that the voltage drop across each diode is 2V when it turns ON. One can experiment with the oscillation frequency by changing the values of R1, R2, R3, and C1. The brightness of the LEDs can also be changed by changing the values of the resistor R4. However, always ensure that the current through the LEDs is not exceeded or else the LEDs will be damaged.

Simple TPS108x Versatile Boost Converter

This is a design circuit of the Versatile Boost Converter circuit using TPS108x. The TPS1081 has chosen because it is suitable for application that requires up to 20 V and 100 mA to drive each column of a passive-matrix OLED (PMOLED). The TPS61080 is suitable for application that requires less than 10 V and only tens of milliamps per column for the active-matrix OLED (AMOLED). This is the figure of the circuit;


The TPS61081 and TPS61080 require input voltages as low as 2.5 V and have adjustable outputs of up to 27 V. Current limit rating of the integrated power switches is the different of The TPS61081 and TPS61080 (typically 1.3 A and 0.5 A, respectively).

The TPS6108x boost converters have constant pulse-width-modulation (PWM) frequency and a traditional current-mode-control scheme for low-noise operation. Besides that, it has additional feature such as n adjustable reference voltage, high efficiency and redundant protection circuits—all of which make the TPS6108x ideal for boosting the 3.6-V Li-ion battery voltage used in most portable applications. The converter can also be used to power higher voltage application such as camera flashlights, OLED displays, WLED backlights and thin film-transistor (TFT) LCDs.

The switching frequency of the converter can be configured to 600 kHz for light-load efficiency or 1.2 MHz for smaller, external components. The 3 × 3-mm QFN package can enable an extremely small boost converter for a wide variety of applications because it has internal power switches, integrated feedback compensation and fast PWM switching. For example, a 24- or 12-V or industrial power rail from a 5-or 3.3-V bus.

[Circuit Source: Texas Instruments Application Note]

Simple Code Lock Circuit

This is Simple Code Lock circuit. This circuit will turn on a relay when the 8-way DIP switches receives the correct code. This is the figure of the circuit;


There are two different types of DIP, they are piano-key DIP sw and 8-way DIP sw. This circuit will not draw the current if the switch is kept off. This circuit can give 256 different combination because the combination is in binary. So it would be very difficult for a burglar to keep up with the settings of the switches.

[Schematic circuit source: talkingelectronics.com]

Simple Broken Charger Circuit

This circuit can be useful to detect if the load of any battery charger or plug-in adaptor supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device. The circuit can safely operate over a 3 to 15V range and 1A max. current, provided the supply voltage is about one volt higher than the voltage required by the load. This circuit is the figure of the circuit;


The circuit is inserted between the supply and the load, therefore, until a trickle-charging current of at least 100µA is flowing towards the load, D1 and D2 will conduct. The forward voltage drop (about 1V) available across the Diodes, drives Q2 into conduction and, consequently, Q1 will be cut-off. If no appreciable load is connected across the circuit's output, Q2 will become cut-off, Q1 will conduct and the Piezo-sounder will beep.

Parts:
R1______________10K 1/4W Resistor
R2_______________1K 1/4W Resistor
R3_______________1K 1/4W Resistor (Optional, see Notes)

D1,D2________1N4007 1000V 1A Diodes
D3______________LED Red (Optional, see Notes)

Q1,Q2_________BC557 45V 100mA PNP Transistors

Simple AM Signal Catcher Circuit

This is a very simple design and easy to build circuit of AM modulation monitoring for HAM transmitters. This is the figure of the circuit;

This circuit is only build by diode and capacitor. You don't have to make any connection with the transmitter only you have to do is that place the coil L1 near the final tank of antenna matching inductor until you hear the signal in the headphones. The circuit is very simple containing only four parts. L1 = coil 3 turns on 1.5 inch diameter former use any guage wire.