AD8304 Analog Devices, AD8304 Datasheet - Page 19

• Manufacturer Part Number: AD8304
• Description: 160 DB Logarithmic Amplifier With Photo-diode Interface
• Manufacturer: Analog Devices

Component
V
SW1, R10
R1, R2
R3, R4
R5, R6, R7, R8, R9
C1, C2, C3, C4, C9
C10
C5, C6, C7, C8, R11,
R12, R13, R14
R15, C11
LK1, LK2
P
, V
N
, AGND
Function
Positive and Negative Supply and Ground Pins
Device Enable: When SW1 is in the “0” position, the PWDN pin is
connected to ground and the AD8304 is in its normal operating mode.
Buffer Amplifier Gain/Slope Adjustment: The logarithmic slope
of the AD8304 can be altered using the buffer’s gain-setting
resistors, R1 and R2.
Intercept Adjustment: A dc offset can be applied to the input
terminals of the buffer amplifier to adjust the effective logarithmic
intercept.
Bias Adjustment: The voltage on the VSUM and INPT pins can
be altered using appropriate resistor values.
Supply Decoupling Capacitors
Photodiode Biaser Decoupling: Provides high-frequency
decoupling of the adaptive bias output at Pin VPDB.
Output Filtering: Allows implementation of a variety of filter
configurations, from simple RC low-pass filters to three-pole
Sallen and Key.
Input Filtering: Provides essential HF compensation at the
input Pin INPT.
Guard/Shield Options: The shells of the SMA connectors
used for the input and the photodiode bias can be set to the
voltage on the VSUM pin or connected to ground.
Table V. Evaluation Board Configuration Options
R4 = Open (Size 0603)
Default Condition
Not Applicable
SW1 = Installed
R10 = 10 kΩ (Size 0603)
R1 = Open (Size 0603)
R2 = 0 Ω (Size 0603)
R3 = Open (Size 0603)
R5 = R6 = Open (Size 0603)
R7 = R8 = Open (Size 0603)
R9 = Open (Size 0603)
C1 = C4 = 0.1 µF (Size 0603)
C2 = C3 = 1 nF (Size 0603)
C9 = 10 nF (Size 0603)
C10 = 0.1 µF (Size 0603)
R11 = R13 = 0 Ω (Size 0603)
R12 = Open (Size 0603)
R14 = 0 Ω (Size 0603)
C5 = C6 = Open (Size 0603)
C7 = C8 = Open (Size 0603)
R15 = 750 Ω (Size 0603)
C11 = 1 nF (Size 0603)
LK1 = Installed
LK2 = Open
AD8304