| 摘要 |
1,185,531. Circuit assemblies; resistors. INTERNATIONAL BUSINESS MACHINES CORP. 17 March, 1967 [30 March, 1966], No. 12523/67. Headings H1R and H1S A micro-module circuit comprising active and passive elements is adjusted to a predetermined D.C. operating point by trimming one of the elements to alter its impedance, monitoring the D.C. output current of the circuit and terminating the impedance altering when the operating point of the circuit reaches a predetermined D.C. operating point. In one embodiment, Figs. 4, 5, a D.C. differential amplifier is provided with three printed trimming resistors 28, 29, 24. To eliminate mismatch in the collector currents of transistors 22, 23 caused by inherent differences in the transistor characteristics a precision resistor 32 having a value equal to that of a sense line is connected between the bases and a voltmeter 33 is connected between the collectors, the voltmeter being shunted by two equal precision resistors 34, 35. If the collector current of one of the transistors is greater than the other this is detected by voltmeter 33. A monitoring circuit including amplifier 38 produces an output signal which controls abrasive control 41 of trimmer 42 that regulates flow of abrasive material from nozzle 43 to cut a path or notch in variable resistor 28, assuming that the collector current from 22 is greater than that from transistor 23, to increase the resistance value of 28 until the voltage drops across standard resistors 34, 35 are equal, forcing the abrasion process to halt. The collector currents are then balanced. In order to adjust the total collector current of the amplifier to its predetermined D.C. operating point the circuit of Fig. 5 is employed whereby the voltage drop across an external precision resistor 36 is compared with a standard reference voltage from Zener diode 46 and the value of resistor 24 is trimmed until the drop across resistor 36 is the same as the voltage drop across Zener diode 46 forcing cessation of the abrasive mechanism 42. In order to compensate for thermal disturbances caused during the abrasive operation a constant current source and a low value compensating resistor are connected in parallel with the voltmeter of Fig. 4 causing a compensating voltage to back out some of the voltage monitored Fig. 8 (not shown). The micro-miniature module comprises a ceramic substrate on which is silk screened a metallic conductive pattern and then trimming resistors 24, 28, 29 are silk screen printed on the top surface of the substrate, Fig. 6 (not shown), and resistors 26, 27 are printed on the bottom surface, Fig. 7 (not shown). The two circuits are interconnected by pins passing through the substrate and the resistors trimmed to their nominal values, that of 24 being well below its expected final value. Transistor chips are then fastened to the top surface of the substrate. |
