Archive for February, 2013

The two variable resistors in DS3902 are used to set bias and modulation currents. The settings are done through I2C* interface. Some modules may require additional EEPROM. This is typically used for serial ID information, and new modules may need to include this feature. DS3902 has programmable address, therefore connecting it to a single I2C bus line (with other devices) without any additional components.

Figure 1 shows connection details for using DS3902 and a serial EEPROM (ATmel AT24C02) on a common I2C interface. Also Figure1 illustrates connections to a laser driver.

Figure1. Schematic for LD, DS3902, and AT24C02.

The DS3902’s default address is A2h (Add_sel = 0). If an address different from A2h is required, Add_sel will be pulled high. Register 00h content is the device address when Add_sel = 1. In the above schematic AT24C02 is configured for A0h address, (A0 = A1 = A2 = 0).

The WP (write-protect) pin connects to ground using a link, allowing R/W access to memory locations. Once the memory is programmed, the WP pin can be pulled high through LK1, to prevent accidental write. DS3902 has S/W protection scheme, whereby access to memory is only possible with password.

The choice of laser driver depends on the specific application and there are a number of Maxim laser drivers to choose from.


MMBT3904 is designed as a general purpose amplifier and switch. The useful dynamic range extends to 100 mA as a switch and to 100 MHz as an amplifier. Sourced from Process 23.As complementary types the PNP transistors MMBT3906 is recommended.



Uses RCA CA3046 IC IF amplifier connected as highly linear voltage-controlled oscillator, in phase-locked loop configuration capableof handling 10.7-MHz amplitude-limited FM input as FM demodulator.Output AF signal is about 20 mV for 75-kHz deviation. FET serves as synchronouschopper type of phase-sensitive detector.

The diagram shows the circuit of the desktop power supply. Regulator IC LM317T is arranged in its standard application. Diode D1 guards against polarity reversal and capacitor C1 is an additional buffer. The green LED (LED1) indicates the status of the power input. Diode D2 prevents the output voltage from rising above the input voltage when a capacitive or inductive load is connected at the output. Similarly, capacitor C3 suppresses any residual ripple.

Connect a standard digital voltmeter in parallel with the output leads to accurately set the desired voltage with the help of variable resistor VR1. You can also use your digital multimeter if the digital voltmeter is not available. Switch on S1 and set the required voltage through preset VR1 and read it on the digital voltmeter.
Now the power supply is ready for use.

The circuit can be wired on a common PCB. After fabrication, enclose the circuit in a metallic cover. Then open the cabinet of your PC and connect the input line of the gadget to a free (hanging) four-pin drive power connector of the SMPS carefully.

4 Channel Audio Mixer circuit



using TL084, 74HC4052, LM31B, 74HC000, 74HC73-2, LM6361N, 1N4148


Parts List:

R1,R6,R11 = 10K

R2,R9 = 1K8

R3 = 100 ohm

R4,R8 = 1K

R5 = 22K

R7 = 1M

*R10 = 0.003 ohm

R12 = 3K9

R13 = 100K

R14 = 10 ohm/1 Watt

P1 = 20K (Frequency adjust)

P2 = 10K (Duty Cycle)

P3 = 1K (Current Limiting)

C1 = 1000uF, 64V

C2 = 10nF, polyester

C3 = 100uF, 64V

C4 = 22nF

C5 = 47uF, 35V

D1,D2 = 1N4004

U1 = LM7810, volt regulator

U2 = LM324, Op-amp

Q1 = IRFP064N, IRFZ44, etc. MOSFet


A very simple with a compact design FM stereo decoder schematic circuit can be designed using the TDA7388 IC manufactured by ST Microelectronics .
The TDA7338 is a monolithic integrated stereo decoder with noise blanking for FM car radio applications.
With the used BICMOS technique, the 19KHz Notch Filter, the PLL Filter and Phase Filter is realized on the chip with a Switched Capacitor concept.
The TDA7338 stereo decoder contains all necessary functions for processing the MPX signal.
The only external component needed for the PLL is the ceramic resonator for the oscillator which runs at 456kHz.

The pilot detector output is designed as an open collector output, therefore an external pull up resistor is needed. To force the decoder to “MONO” Pin 19 has to be clamped to a voltage below 0.8V.
Selecting VCO-OFF (Pin 7 to GND) the VCO is switched off and the SB and HCC are disabled.
This TDA7338 receiver circuit needs to be powered by a 9 volts DC power supply .

The VIPER12A combines a dedicated current mode PWM controller with a high voltage power MOSFET on the same silicon chip.

Typical applications cover off line power supplies for battery charger adapters, standby power supplies for TV or monitors, auxiliary supplies for motor control, etc.

The internal control circuit offers the following benefits: Large input voltage range on the VDD pin accommodates changes in auxiliary supply voltage (This feature is well adapted to battery charger adapter configurations), automatic burst mode in low load condition and overvoltage protection in HICCUP mode.

Fixed 60 kHz switching frequency
9 V to 38 V wide range VDDvoltage
Current mode control
Auxiliary undervoltage lockout with hysteresis
High voltage start-up current source
Overtemperature, overcurrent and overvoltage protection with auto-restart
Typical power capability
European (195 – 265 Vac) 8 W for SO-8, 13 W for DIP-8
European (85 – 265 Vac) 5 W for SO-8, 8 W for DIP-8

The UTC20N60 is an N-channel enhancement mode power MOSFET using UTC’s advanced technology to provide customers with planar stripe and DMOS technology. This technology is specialized in allowing a minimum on-state resistance and superior switching performance. It also can withstand high energy pulse in the avalanche and commutation mode.


The UTC 20N60 is universally applied in motor control, UPS, DC choppers and switch-mode and resonant-mode power supplies.


The 74HC14D is a hex inverting schmitt trigger. The 74HC14D is a high-speed Si-gate CMOS device and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC14D provides six inverting buffers with Schmitt-trigger action. They are capable of transforming slowly changing input signals into sharply defined, jitter-free output signals.
74HC14D absolute maximum ratings: (1)VCC supply voltage: -0.5 +7 V; (2)IIK input diode current VI < -0.5 V or VI > VCC + 0.5 V: ±20 mA; (3)IOK output diode current VO < -0.5 V or VO > VCC + 0.5 V: ±20 mA; (4)IO output source or sink current: -0.5 V < VO < VCC + 0.5 V – ±25 mA; (5)ICC; IGND VCC or GND current: – 50 mA; (6)Tstg storage temperature: -65 +150℃.
74HC14D features: (1)Complies with JEDEC standard no. 7A; (2)ESD protection: HBM EIA/JESD22-A114-A exceeds 2000 V; MM EIA/JESD22-A115-A exceeds 200 V; (3)Specified from -40 to +85℃ and -40 to +125℃.