Datasheet

I =
EXT
2V (V V )
50k
- -
W
OCM S+ S-
V
S+
V
OCM
V
S-
100kW
100kW
I
EXT
Tointernal
V circuit
OCM
THS452x
R
G
R
F
R
O
R
O
R
G
R
F
R
IT
R
IT
V
S-
V
OCM
V
IN+
PD
Optional;
installedto
balance
impedanceseen
at V
IN+
V
OCM
Control
PD Control
V
OUT-
V
OUT+
V
S+
0.22 Fm
0.22 Fm
THS4521
THS4522
THS4524
SBOS458F –DECEMBER 2008–REVISED SEPTEMBER 2011 www.ti.com
Figure 62 represents the V
OCM
input. The internal Single-Supply Operation
V
OCM
circuit has typically 23 MHz of –3 dB bandwidth,
To facilitate testing with common lab equipment, the
which is required for best performance, but it is
THS4521EVM allows for split-supply operation; most
intended to be a dc bias input pin. A 0.22-μF bypass
of the characterization data presented in this data
capacitor is recommended on this pin to reduce
sheet is measured using split-supply power inputs.
noise. The external current required to overdrive the
The device can easily be used with a single-supply
internal resistor divider is given approximately by the
power input without degrading performance.
formula in Equation 2:
Figure 63 shows a dc-coupled single-supply circuit
with single-ended inputs. This circuit can also be
applied to differential input sources.
where:
• V
OCM
is the voltage applied to the V
OCM
pin (2)
Figure 62. V
OCM
Input Circuit
Typical Performance Variation with Supply
Figure 63. THS4521 DC-Coupled Single-Supply
Voltage
with Single-Ended Inputs
The THS4521, THS4522, and THS4524 family of
devices provide excellent performance across the
The input common-mode voltage range of the
specified power-supply range of 2.5 V to 5.5 V with
THS4521, THS4522, and THS4524 family is
only minor variations. The input and output voltage
designed to include the negative supply voltage. in
compliance ranges track with the power supply in
the circuit shown in Figure 63, the signal source is
nearly a 1:1 correlation. Other changes can be
referenced to ground. V
OCM
is set by an external
observed in slew rate, output current drive, open-loop
control source or, if left unconnected, the internal
gain, bandwidth, and distortion. Table 3 shows the
circuit defaults to midsupply. Together with the input
typical variation to be expected in these key
impedance of the amplifier circuit, R
IT
provides input
performance parameters.
termination, which is also referenced to ground.
Note that R
IT
and optional matching components are
added to the alternate input to balance the
impedance at signal input.
Table 3. Typical Performance Variation versus Power-Supply Voltage
PARAMETER V
S
= 5 V V
S
= 3.3 V V
S
= 2.5 V
–3-dB Small-signal bandwidth 145 MHz 135 MHz 125 MHz
Slew rate (2-V step) 490 V/μs 420 V/μs 210 V/μs
Harmonic distortion at 1 MHz, 2 V
PP
, R
L
= 1 kΩ
xxxSecond harmonic –85 dBc –85 dBc –84 dBc
xxxThird harmonic –91 dBc –90 dBc –88 dBc
Open-loop gain 119 dB 116 dB 115 dB
Linear output current drive 55 mA 35 mA 24 mA
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Product Folder Link(s): THS4521 THS4522 THS4524