TPS61160/1 with 40-V rated integrated switch FET is a boost converter that drives up to 10 LEDs in series. The boost converter is used to reduce output ripple, improve conversion efficiency, and allows for the use of small external components. The default white LED current is set with the external sensor resistor Rset, and the feedback voltage is regulated to 200mV. 1-wire digital interface through the CTRL pin can control the LED current during the operation. Another way, a pulse width modulation (PWM) signal can be applied to the CTRL pin through which the duty cycle determines the feedback reference voltage. The device features integrated open LED protection that disables the TPS1160/1 to prevent the output from exceeding the absolute maximum ratings during open LED condition is the maximum protection.

This device has some features such as:

• 2.7V to 18V Input Voltage Range
• 26V Open LED Protection for 6 LEDs (TPS61160)
• 38V Open LED Pretection for 10 LEDs (TPS61161)
• 200mV Reference Voltage With +- 2% Accuracy
• Flexible Digital and PWM Brightness Control
• Built-in Soft Start
• Up to 90% Efficiency
• 2mmx2mmx0.8mm 6-pin QFN Packacge With Thermal Pad

And can be used in application such as:
Cellular Phones, Portable Media Players, Ultra Mobile Devices, GPS Receivers, White LED Backlighting for Media Form Factor Display. [Source: Texas Instruments Application Note]

Low impedance gate drive to the 2N3970 analog switch for both on and off drive conditions is provided by this commutator. By producing a low ac impedance for off drive and high ac impedance for on drive to the 2N3970, this commutator circuit can close enough to the ideal gate drive conditions for high frequency signal handling. We use LH0005 as a megahertz signals amplifier.

Here’s the circuit diagram:

[Source: National Semiconductor Application Note]

The benefits of 4-20mA current loop format in process control systems are 2-wire sensor operation, long cable runs, and noise immunity.  The voltages  for the loop can be ranging from 12VDC to 40VDC and  are inherently nonratiometric to the output signal. The MAX1452 low current consumption allows the system to operate from loop  power with a simple  4-20mA circuit drives. Here’s the circuit diagram:

The MAX1452 is equipped with five 16-bit internal calibration registers that can be loaded from the serial digital interface or from EEPROM. You can get more information about MAX1452 at http://datasheets.maxim-ic.com/en/ds/MAX1452.pdf .