UG-865

ADA4530-1R-EBZ User Guide

Rev. 0 | Page 8 of 14

TRANSIMPEDANCE WITH 10 GΩ SMT FEEDBACK

RESISTOR AND IN+ CONNECTED TO GROUND

(ADA4530-1R-EBZ-TIA)

On the ADA4530-1R-EBZ-TIA board, the amplifier is defaulted

to a transimpedance configuration. The transimpedance

configuration is a current-to-voltage (I to V) converter. A

10 GΩ SMT 1206 package size feedback resistor (RF1) is pre-

assembled on board. If other resistor values or package sizes are

needed, the 10 GΩ feedback resistor can be desoldered to allow

the assembly for the SMT resistor of choice. The evaluation

board provides a combination footprint that allows assembly of

either an 0805, 1206, 1210, 2510, or 2512 package size for RF1.

Larger value through hole feedback resistors, in the order of high

gigaohms or teraohms, are also often used in a transimpedance

application. This option is discussed in the Transimpedance

with Through Hole Feedback Resistor section.

Table 6. Transimpedance with 10 GΩ SMT Feedback

Resistor and IN+ Connected to Ground Pad/Connector

Configuration

Pad/Connector

Description

JP2

0 Ω

JP3

Unconnected

RF1

10 GΩ

RS1

0 Ω

RF1

10GΩ

RS1

0Ω

JP2

0Ω

Figure 13. Transimpedance with 10 GΩ Feedback and IN+

Connected to Ground

U1

RO

499Ω

RF1

10GΩ

JP2

0Ω

RS1

0Ω

V+

V–

J1

(BNC)

INPUT

J2

(BNC)

OUTPUT

Figure 14. Transimpedance with 10 GΩ Feedback and IN+

Connected to Ground Schematic

TRANSIMPEDANCE WITH THROUGH HOLE

FEEDBACK RESISTOR

In a transimpedance configuration, larger value through hole

feedback resistors, in the order of high gigaohms or teraohms,

are often used. These resistors are glass encapsulated and

hermetically sealed, and come in large footprints. An example

of this is the Ohmite RX-1M ultrahigh resistance, high stability,

hermetically sealed resistor.

To cater to its large footprint, pin sockets (P7 and VOUT) are

provided for RF2. Place one end of the leaded resistor at P7 and

the other end at VOUT. Note that when using the evaluation

board for this configuration, use the ADA4530-1R-EBZ-TIA

board and remove the pre-assembled 10 GΩ feedback resistor.

When RF2 is used, remove the cover of SHIELD1 to allow

placement of the large through hole resistor. Secure SHIELD3,

which is provided with the kit, with the pre-assembled RF clips

to provide electrostatic shielding.

Table 7. Transimpedance with Through Hole Feedback

Pad/Connector

Description

JP2

0 Ω

JP3

Unconnected

RS1

0 Ω

RF1

Remove from board

RF2

Populate with resistor of choice

JP2

0Ω

RF2

GΩ/TΩ

RS1

0Ω

Figure 15. Transimpedance with Through Hole Feedback Resistor

J1

(BNC)

INPUT

J2

(BNC)

OUTPUT

U1

RO

499Ω

RF2

THROUGH HOLE

JP2

0Ω

RS1

0Ω

V+

V–

Figure 16. Transimpedance with Through Hole Feedback Resistor Schematic