AD8336ACPZ-R7 datasheet(23/28 Pages) AD

23 / 28 page

AD8336

Rev. 0 | Page 23 of 28

APPLICATIONS

AMPLIFIER CONFIGURATION

The AD8336 amplifiers can be configured in various options.

In addition to the 60 dB gain range variable gain stage, an

uncommitted voltage gain amplifier is available to the user as a

preamplifier. The preamplifier connections are separate to

enable noninverting or inverting gain configurations or the use

of interstage filtering. The AD8336 can be used as a cascade

connected VGA with preamp input, as a standalone VGA, or as

a standalone preamplifier. This section describes some of the

possible applications.

VOUT

VGAI

PRAO

GNEG

AD8336

VCOM

VPOS

GPOS

34dB

PrA

PWRA

ATTENUATOR

–60dB TO 0dB

GAIN CONTROL

INTERFACE

INPP 4

INPN

–

BIAS

VNEG

Figure 79. Application Block Diagram

PREAMPLIFIER

While observing just a few constraints, the uncommitted

voltage feedback preamplifier of the AD8336 can be connected

in a variety of standard high frequency op amp configurations.

The amplifier is optimized for a gain of 4×, (12 dB) and has a

gain bandwidth product of 600 MHz. At a gain of 4×, the

bandwidth is 150 MHz. The preamplifier gain can be adjusted

to a minimum gain of 2×; however, there will be a small peak in

the response at high frequencies. At higher preamplifier gains,

the bandwidth diminishes proportionally in conformance to the

classical voltage gain amplifier GBW relationship.

While setting the overall gain of the AD8336, the user needs to

consider the input referred offset voltage of the preamplifier.

Although the offset of the attenuator and postamplifier are

almost negligible, the preamplifier offset voltage, if uncorrected,

is increased by the combined gain of the preamplifier and

postamplifier. Thus for a maximum gain of 60 dB, an input offset

voltage of only 200 μV results in an error of 200 mV at the output.

Circuit Configuration for Noninverting Gain

The noninverting configuration is shown in Figure 80. The

preamp gain is described by the classical op amp gain equation

Gain

The practical gain limits for this amplifier are 6 dB to 26 dB.

The gain bandwidth product is about 600 MHz, so that at 150

MHz, the maximum achievable gain is 12 dB (4×). The minimum

gain is established internally by fixed loop compensation, and is

6 dB (2×). This amplifier is not designed for unity gain operation.

Table 5 shows the gain bandwidth for the noninverting gain

configuration.

PRAO

CIRCUIT CONFIGURATION FOR NONINVERTING GAIN

34dB

AD8336

PREAMPLIFIER

–60dB TO 0dB

INPP

INPN

GAIN = 12dB

RFB1

100Ω

VGAI

VPOS

VNEG

+5V

–5V

PWRA

VCOM

RFB2

301Ω

VOUT

Figure 80. Circuit Configuration for Noninverting Gain

The preamplifier output reliably sources and sinks currents up

to 50 mA. When using ±5 V power supplies, the suggested sum

of the output resistor values is 400 Ω total for the optimal trade-

off between distortion and noise. Much of the low gain value

device characterization was performed with resistor values of

301 Ω and 100 Ω, resulting in a preamplifier gain of 12 dB (4×).

With supply voltages between ±5 V and ±12 V, the sum of the

output resistance should be increased accordingly and a total

resistance of 1 kΩ is recommended. Larger resistance values,

subject to a trade-off in higher noise performance, can be used

if circuit power and load driving is an issue. When considering

the total power dissipation, remember that the input ladder

resistance of the VGA is part of the preamp load.

Table 5. Gain vs. Bandwidth for Noninverting Preamplifier

Configuration.

Preamp Gain

Numerical

Preamp BW

(MHz)

Composite

Gain (dB)

4×

150

−14 to +46

8×

−8 to +52

16×

−2 to +58

20×

0 to 60

AD8336ACPZ-R7 数据表(PDF) 23 Page - Analog Devices

AD8336ACPZ-R7 数据表(HTML) 23 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

数据表下载

链接网址

AD8336ACPZ-R7 数据表(PDF) 23 Page - Analog Devices

AD8336ACPZ-R7 数据表(HTML) 23 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

数据表 下载

链接网址

数据表下载