Electronic Design


Amplifier IC Boasts Less Than 100-µA Quiescent Current Per Channel
Apex Microtechnology Corp.
(520) 690-8600; www.apexmicrotech.com

The MA32 is a precision 32-channel, high-voltage amplifier IC housed in a 240-pin quad flat pack (QFP). It features less than 100 µA of quiescent current per channel. Also, its footprint measures less than 1.5 in2.

The MA32 drastically reduces the board space requirements in switching circuitry that can include more than 1000 3D mirror arrays requiring two amplifier drivers per channel per mirror. It features high-voltage operation up to 300 V. The output voltage is up to 290 V per channel. This IC is designed for independent channel operation using the output of a digital-to-analog converter (DAC) to drive each input. It also drives capacitive loads in MEMS-based optical-switch applications. The gain for each driver is internally set for 50 V/V.

Available now, the MA32 in the QFP costs $149.70.

CMOS Op Amps Feature 200-MHz Gain-Bandwidth
Texas Instruments Inc.
(800) 477-8924, ext. 4500; www.ti.com

The OPA355 operational amplifiers are the industry's fastest CMOS op amps. These devices feature a 200-MHz gain-bandwidth and a 360-V/µs slew rate. The OPA355 combines low-voltage operation and rail-to-rail output. Also, these op amps feature digital shutdown at a low cost.

These op amps suit wide-bandwidth applications requiring exceptional ac performance. The voltage-feedback devices are unity-gain stable and can drive an output current of ±100 mA. Bandwidth in unity gain is 450 MHz. Low differential gain and phase error are ideal for demanding video-processing applications. All versions (single, dual, and triple) have a digital shutdown function, providing power savings during idle periods. It also places the output in a high-impedance state to support output multiplexing. The op amps are optimized for operation on single or dual supplies ranging from 2.5 to 5.5 V. The common-mode input range extends from 100 mV below ground up to 1.5 V from the positive supply. Output swing is within 100 mV of the rails. Additional features include low noise, low input bias current (3 pA), and low quiescent current (8.3 mA per channel).

The OPA355 (single) is available in SOT23-6 and SO-8 packages and costs $1.19. The OPA3355 (triple) is packaged in TSSOP-14 and SO-14 packages and costs $2.79. All pricing is for 1000-unit quantities.

PSRR Audio Amplifiers Target Cellular Phone Market
National Semiconductor Corp.
(408) 721-5000; www.national.com

The LM4894 and LM4895 Boomer audio amplifiers are optimized for the cellular phone market. Both devices deliver superior power-supply rejection ratio (PSRR) performance. With the input terminated with a 10-Ω resistive load, the LM4894 and LM4895 deliver 80-dB PSRR at 217 Hz at 3 V. With the input unterminated, the LM4894 and LM4895 deliver 87 dB PSRR at 217 Hz at 3 V.

The devices deliver 50 dB of common-mode rejection ratio (CMRR). Both the LM4894 and LM4895 also feature a selectable shutdown mode. This feature enables engineers to select either shutdown logic high or shutdown logic low. The LM4894/95 are optimized to save power by operating at a low supply voltage (3 V). They still provide sufficient output power (350 mW, 8 Ω, <1% THD), suitable for normal listening and speakerphone and ringer-tone amplification. In the LM4894, the input coupling is eliminated to reduce pop and click noise at turn-on and turn-off. It also features an internal thermal-shutdown protection mechanism. The LM4895's fully differential design and 6-dB fixed gain yield the simplest audio amplifier solution.

Both devices are available now in a nine-bump micro SMD, 10-pin LLP, and 10-pin MSOP packaging. In 1000-unit quantities, the LM4894 and LM4895 cost $0.80 and $0.83, respectively.

FPAA Configuration Software Adds Filter Synthesis
Anadigm Inc
(866) 240-8806; fax (480) 344-5277; www.anadigm.com

Filter synthesis has now been added to field-programmable analog array (FPAA) configuration software. The FilterDesigner tool provides an extremely versatile means of specifying high-order classical filters. It also enables the combination of filters with additional signal-conditioning circuitry to implement single-chip analog solutions.

In its default mode, FilterDesigner v1.0 offers Bode plot views of filter response for high-pass, low-pass, bandpass, and band-stop filters. Also, linear amplitude and linear phase plots are available. Butterworth, Chebyshev, Inverse Chebyshev, or Elliptic approximations may be employed to create the desired response. Users specify the characteristics of the filter effect that they seek in terms of high-level parameters such as corner frequencies and pass-band gain.

The tool automatically constructs the required circuit. It then decomposes the circuit into the filter stages and settings required for implementation using the general-purpose array structure of the FPAA. The software will create filters of any complexity, but will alert users if the filter design is beyond the capacity of the first generation of FPAAs. This upper limit depends on the bandwidth and can reach as high as a twentieth-order filter in a single chip.

FilterDesigner is free with the latest version of the company's configuration software for FPAAs. It can be downloaded from the company's Web site.

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