Analog Devices

The AD8351 is a low cost differential amplifier useful in RF and IF applications up to 2.2 GHz. The voltage gain can be set from unity to 26 dB using a single external gain resistor. The AD8351 provides a nominal 150 Ω differential output impedance. The excellent distortion performance and low noise characteristics of this device allow for a wide range of applications.The AD8351 is designed to satisfy the demanding performance requirements of communications transceiver applications. The device can be used as a general-purpose gain block, an ADC driver, and a high speed data interface driver, among other functions. The AD8351 can also be used as a single-ended-to-differential amplifier with similar distortion products as in the differential configuration. The exceptionally good distortion performance makes the AD8351 an ideal solution for 12-bit and 14-bit IF sampling receiver designs.Fabricated in Analog Devices, Inc., high speed XFCB process, the AD8351 has high bandwidth that provides high frequency performance and low distortion. The quiescent current of the AD8351 is 28 mA typically. The AD8351 amplifier comes in a compact 10-lead MSOP package or in a 16-lead LFCSP package, and operates over the temperature range of −40°C to +85°C.ApplicationsDifferential ADC driversSingle-ended-to-differential conversionIF sampling receiversRF/IF gain blocksSAW filter interfacingAvailabilityOther RF / IF amplifiers products:AD8367- 500 MHz Single Ended, Analog Controlled VGAAD8369- 600 MHz, 45 dB Digitally Controlled Variable Gain AmplifierAD8350- 1.0 GHz Differential Amplifier

The AD8361 is a mean-responding power detector for use in high frequency receiver and transmitter signal chains, up to 2.5 GHz. It is very easy to apply. It requires a single supply only between 2.7 V and 5.5 V, a power supply decoupling capacitor, and an input coupling capacitor in most applications. The output is a linear-responding dc voltage with a conversion gain of 7.5 V/V rms. An external filter capacitor can be added to increase the averaging time constant.The AD8361 is intended for true power measurement of simple and complex waveforms. The device is particularly useful for measuring high crest-factor (high peak-to-rms ratio) signals, such as CDMA and W-CDMA. The AD8361 has three operating modes to accommodate a variety of analog-to-digital converter requirements:Ground reference mode, in which the origin is zero.Internal reference mode, which offsets the output 350 mV above ground.Supply reference mode, which offsets the output to VS/7.5.The AD8361 is specified for operation from −40°C to +85°C and is available in 8-lead MSOP and 6-lead SOT-23 packages. It is fabricated on a proprietary high fTsilicon bipolar process.

The AD8362 is a true rms-responding power detector that has a 65 dB measurement range. It is intended for use in a variety of high frequency communication systems and in instrumentation requiring an accurate response to signal power. It is easy to use, requiring only a single supply of 5 V and a few capacitors. It operates from arbitrarily low frequencies to over 3.8 GHz and accepts inputs from −52 dBm to +8 dBm with crest factors that are typical of quadrature amplitude modulation (QAM) and orthogonal frequency division multiplexing (OFDM) modulation schemes.The input signal is applied to a resistive ladder attenuator that comprises the input stage of a variable gain amplifier (VGA). The 12 tap points are smoothly interpolated using a proprietary technique to provide a continuously variable attenuator, which is controlled by a voltage applied to the VSET pin. The resulting signal is applied to a high performance broadband amplifier. Its output is measured by an accurate square-law detector cell. The fluctuating output is then filtered and compared with the output of an identical squarer, whose input is a fixed dc voltage applied to the VTGT pin, usually the accurate reference of 1.25 V pro-vided at the VREF pin.The difference in the outputs of these squaring cells is integrated in a high gain error amplifier, generating a voltage at the VOUT pin with rail-to-rail capabilities. In a controller mode, this low noise output can be used to vary the gain of a host system’s RF amplifier, thus balancing the setpoint against the input power. Optionally, the voltage at VSET can be a replica of the RF signal’s amplitude modulation, in which case the overall effect is to remove the modulation component prior to detection and low-pass filtering. The corner frequency of the averaging filter can be lowered without limit by adding an external capacitor at the CLPF pin. The AD8362 can be used to determine the true power of a high frequency signal having a complex low frequency modulation envelope, or simply as a low frequency rms volt-meter. The high-pass corner generated by its offset-nulling loop can be lowered by a capacitor added on the CHPF pin.Used as a power measurement device, VOUT is strapped to VSET. The output is then proportional to the logarithm of the rms value of the input. In other words, the reading is presented directly in decibels and is conveniently scaled 1 V per decade, or 50 mV/dB; other slopes are easily arranged. In controller modes, the voltage applied to VSET determines the power level required at the input to null the deviation from the setpoint. The output buffer can provide high load currents.The AD8362 has 1.3 mW power consumption when powered down by a logic high applied to the PWDN pin. It powers up within about 20 μs to its nominal operating current of 20 mA at 25°C. The AD8362 is supplied in a 16-lead TSSOP for operation over the temperature range of −40°C to +85°C.ApplicationsPower amplifier linearization/control loopsTransmitter power controlsTransmitter signal strength indication (TSSI)RF instrumentation