Features Frequency Range:
DC to 1MHz Frequency Response: <±0.1dB Distortion: <0.1% Maximum Voltage: 140Vrms, OC Voltage Gain: 0dB to 40dB Variable DC Offset: 0V to 200V Peak Short-Circuit Protection
Options Rack Mounting Kit: Part no. RK-519,
permits installation of the
Model 3900 into
a standard 19" rack spacing. Extended 1 Year Warranty: Part No. EW7500.
Accessory
Impedance matching Transformer
Model MT56R
DESCRIPTION The Krohn-Hite
Model 7500 is the first direct-coupled, wideband amplifier that offers extended
output power and voltage capabilities, low distortion, an advanced, all solid
state design, and performance features not previously available.
The Model 7500 provides
more than 75 watts of continuous power (150 watts at dc), and 125V rms from
dc to 100kHz. Frequency response of the 7500 is typically flat to within 0.05dB
over most of its range. In addition, the 7500 typically contributes <0.05%
of total harmonic distortion, at full power output, up to 10kHz. The voltage
gain of the 7500 is non-inverting, and can be selected for either 20dB (10)
or 40dB (100) of fixed gain, or continuously adjustable from 0dB to 40dB.
The 7500 also provides either direct (dc) or capacitive (ac) input coupling.
ADDITIONAL
FEATURES
An additional
feature of the Model 7500 is the variable output dc offset control. With an
ac input signal, the amplifier’s combined ac plus dc offset output is adjustable
from 0V to ±200V peak, open circuit. With no input signal applied, the 7500
provides an adjustable dc voltage of 0V to ±200V open circuit, for use as
an auxiliary DC supply, within the amplifier’s voltage and current limitations.
OUTSTANDING
PERFORMANCE
The outstanding
performance of the Model 7500 is the result of improved techniques in circuit
design, plus the use of all solid-state circuitry. The input stages are designed
to provide a high input impedance, extended bandwidth, and excellent dc and
thermal stability. The output stage is designed with high voltage transistors,
in place of conventional transformer coupling, to provide the 7500 with its
high output and voltage capability, and direct output coupling. The output
transistors are protected from short circuits or other abnormal conditions
on the amplifier’s output, by the use of a modified, fold-back current-limiting
technique. This technique permits the limiting current to vary as a function
of output voltage, load, and frequency. The output stage is convection cooled,
by the use of a unique heat sink arrangement, that provides freedom from noise
caused by conventional fans or blowers.
APPLICATIONS
The Model
7500 is one of the few amplifiers on the market today that offers a combination
of power, performance and versatility. Its power and voltage capability, low
distortion and flat response, make the 7500 well suited for use in precision
meter calibration, transducer driving, bridging applications requiring high
input and low output impedance, and as a low distortion ac power source, when
used with a suitable low distortion oscillator.
SPECIFICATIONS
OUTPUT
(Specifications apply
using a 200 ohm resistive load)
Frequency Range: dc to 1MHz. Power: 75 watts, dc to 100kHz; 40 watts at 500kHz; 10 watts at 1MHz. Voltage: 125V rms, dc to 100kHz; 90V rms at 500kHz; 45V rms at 1MHz. Current: 625mA rms, dc to 100kHz; 450mA rms at 500kHz; 225mA rms at
1MHz. Frequency Response: Flat to within ±0.1dB, dc to 10kHz; ±1.5dB to 500kHz;
–3dB at approximately 1MHz. Harmonic Distortion (at 75 watts into 200 ohms): <0.1% to 10kHz, approximately
1.5% at 100kHz. Voltage Gain: Fixed, 20dB ±0.2dB (X10) or 40dB ±0.2dB (X100), or continuously
variable 0dB to 40dB. Gain Stability: <±0.001dB change for a 10% change in line voltage. Dynamic Range: >85dB. Phase Shift: 0° ±1° from dc to 10kHz. Phase shift increases linearly
to 100° (lagging) at 1MHz. Squarewave Response (at 100Vp-p into 200 ohms): Rise Time: <600ns.
Overshoot: <5%. Zero droop in dc coupled mode.
Regulation: No load to 200 ohms, <0.5%, dc to 10kHz. Hum and Noise (1MHz bandwidth): <4mV rms with input shorted; <10mV
rms with input open and shielded. Coupling: Direct. DC Level: Nominal zero volts. DC Offset (no load): Variable, 0V to ±200V. Combined ac plus dc offset
limited to ±200V. DC Level Stability (After 30 minute warm-up): Vs. Line (short term): <1mV for 10% line voltage change.
Vs. Time: <2mV/8hrs.
Vs. Temperature: < 5mV/°C. Internal Impedance: <1 ohm, dc to 10kHz; <10 ohms at 100kHz; <80 ohms
at 1MHz.
INPUT Maximum
Voltage: ±20V peak in the variable and the X100 GAIN positions; ±200V
peak in the X10 GAIN position. Maximum DC Component: ±200V (except VARIABLE GAIN position) in the
ac position of the INPUT COUPLING switch. Sensitivity: 1.5V rms at maximum gain setting. Coupling: Either direct (dc), or capacitive (ac) with low frequency
cutoff at approximately 1Hz. Impedance: Fixed Gain Modes: 1M ohm in parallel with 85pF.
Variable Gain Mode: 5k ohms.
GENERAL
Load Impedance:
Capable of driving any load within the current and voltage limitations of
the amplifier. Load Power Factor: 1.0 to zero, leading or lagging. Temperature Range: 0°C to 45°C. Controls: Front Panel: POWER switch, 3-position push-button GAIN selector,
variable GAIN control,
3-position push-button DC OFFSET selector, variable OFFSET control,
screwdriver control
for DC output level.
Rear Panel: CHASSIS/FLOATING ground switch. Front Panel Indicators: Power ON, Output OVERLOAD. Terminals: Front Panel: BNC for INPUT, binding posts for OUTPUT.
Rear Panel: BNC for INPUT, binding posts for OUTPUT, ac power receptacle,
chassis ground post. Power Requirements: 105-125 or 210-250 volts, single phase, 50-400Hz,
85 watts quiescent, 400 watts. Fuse Protection: ac line, 5A slow-blow (115V), 2.5A slow-blow (230V);
output stage unregulated supplies, 1A fast-blow (each supply). Dimensions and Weights: 5.25" (13.3cm) high, 16.63" (42.2cm) wide,
17" (43.2cm) deep; 35 lbs. (15.8kg) net, 40 lbs. (18.1kg) shipping. Accessories: 3 terminal line cord; operating manual.
OPTIONS Rack
Mounting Kit: Part No. RK-519 permits the installation of the Model 7500
into a standard 19" rack spacing. Extended 1 Year Warranty: Part No. EW7500.
