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INSTRUCTION MANUAL
MODEL 300
ELECTROMETER
OPERATIONAL AMPLIFIER
MODEL 300 OPERATIONAL AMPLIFIER TABLE OF CONTENTS
TABLE OF CONTENTS
Section Page Section Page
1. GENERAL DESCRIPTION . . . . . . . . 1 4. MAINTENANCE . . . . . . . . . . . 23
l-l. General . . . . . . . . . . . 1 4-l. General . . . . . . , . . 23
l-2. Features . , . . . . . . . . 1 4-2. Maintenance Schedule . . . . 23
l-3. Specifications . , . . + . . 2 4-3. Parts Replacement . . . . . 23
l-4. Operating Modes : , . . , . . 3 4-4. Troubleshooting . . . . . . . 24
1-5. Accessories . . . . . . I . . 3 4-5. Troubleshooting Positive and
l-6. Equipment Shipped . . . ,. . . 3 Negative Power Supply
Regulators . . . . . . . . . 25
2. OPERATION . . . . . . . . . . . . . 5 4-6. Troubleshooting the Amplifier 26
4-7. Calibration . . . . . . . . . 26
2-l. Terminals . . . . . . . . . . 5
2-2. Mounting Instructions . . . 5 5. ACCESSORIES . . . . . . . . . . 29
2-3. power supply . . . . . . . . 6
2-4. Input Connections . . . , . . 7 5-l. Model 3012 Power Supply . . , 29
2-5. Output Connections . . . . . 8 5-2. Model 3011 Shielded Switch . 31
2-6. Modes of Operation . . . . . 8
2-7. Linear Current Amplifier . . 10 6. REPLACEABLE PARTS . . . . . . . . . 35
2-E. Logarithmic Current Amplifier 12
2-9. Current Integrator or 6-l. Replaceable Parts List . . . 35
Charge Amplifier . . . . . . 14 6-2. How to Order Parts . . . . . 35
2-10. Impedance Matching Amplifier 15 Model 300 Replaceable
2-11. Voltage Amplifier . . . . . . 17 Parts List . . . . . . :. 36
2-12. Other Modes of Operation . . 18 Model 3012 Replaceable
2-13. Stability, Frequency Response, Parts List . . . . . . . . 38
Andy Oscillation . . . . . . 18 Model 300 Schematic
Z-14. Remote Zero Control . . . . . 19 Diagram 195581) . . , . . . 4.1
2-15. Connections and Use of Model 3012 Schematic
Reference Voltages . . . . . 20 Diagram 20351B . . . . . . 43
3. CIRCUIT DESCRIPTION . . . . . . . . 21
* Change Notice , . . . . . . . .Last Page
3-l. General . . . . . . . . . . . 21
3-2. Electrometer Input . . . . . 21
3-3. &lid State
Differential Amplifier . . . 21
3-4. Positive Pkvar Supply
Regulator . . . . . . . . . 22 * Yellow Change Notice Sheet is included
3-5. Negative Power Supply only for instrument modifications
Regulator . . . . . . . . . 22 affecting the Instruction Manual.
0167R i
MODEL 300 OPERATIONAL AMPLIFIER GENERAL DESCRIPTION
SECTION 1. GENERAL DESCRIPTION
l-l. GENERAL.
a. The Keithley Model 300 Electrometer Operational Amplifier is a compact, sing&-end-
ed amplifier. It has greater than 1014 ohm input resistance and less than 5 x lo-
ampere current offset. Its current drift is less than lo-l5 ampere/24 hours and its cur-
rent noise is less than 5 x LO-l5 ampere peak-to-peak. Primarily a current amplifier, the
Model 300 will operate with signals from LO-l4 to 10T2 ampere.
b. Open loop dc voltage gain is 20,000; output is fll volts, 11 milliamperes.
C. The Model 300 is completely solid state except for the input stage. Electrometer
input tubes are used because they have less noise, better stability, and are less sensi-
tive to voltage transients than other high impedance devices now available.
l-2. FEATURES.
a. The Model 300 will operate from inexpensive power supplies or batteries. Unregula-
ted supplies with outputs from +16 to 125 volts and -16 to -25 volts will power the Model
300. The Amplifier Will also operate from standard 15-volt regulated supplies.
b. An internal zero control is built into the Model 300. In addition, a potentiometer
can be connected externally to allow remote zeroing.
c. A regulated reference or polarizing potential of ~13.5 volts at 1 milliampere is
available.
d. Electrostatic and electromagnetic
shields are provided to insure minimum pick-
UP. Therefore, input and feedback elements
can be mounted within the Model 300 case
with complete shielding.
e. The Model 300 withstands input over-
loads up to 2400 volts and will not be dam-
aged by induced static voltages with the
input open.
f. An internal compensation network
greatly reduces the possibility of oscil-
lation regardless of external circuitry.
g. The Amplifier is constructed on a
3-l/2 inch by 4 inch prip.ted circuit board
that forms a 15-terminal card-edge con-
nector. The input is a Teflon-insulated
coaxial connector, Space and mounting ter-
minals are provided for internally mounting
input, feedback and output dividing impe- FIGURE 1. Keithley Instruments Model 300
dances. Electrometer Operational Amplifier.
0566R 1
GENERAL DESCRIPTION MODEL 300 OPERATIONAL AMPLIFIER
l-3. SPECIFICATIONS (Measured at 250C).
DC VOLTAGE GAIN,, OPEN LOOP:
Unloaded: Greater than 20,000.
lOOO-ohm load: Greater than 12,000.
INPUT CHARACTERISTICS:
Resistance: Greater than 1014 ohms.
Capacitance: Less than 10 picofarads.
Current Offset: Less than 5 x LO-l4 ampere.
Drift: Less than lo-l5 ampere/24 hours.
Temperature Coefficient: Less than LO-15 ampere/OC.
Voltage Offset: Adjustable to zero.
Drift: Less than 500 microvolts/hour averaged over any 24-hour period after two-'
hour warm-up.*
Temperature Coefficient: Less than 500 microvoltsf