This stage highlighted in red color is formed by Q 1, Q 2, Q 3, Q 4, Q 5, R 1, R 2, R 3, and C 1: 1.2.1 JRC4558 Long Tailed Pair Differential Amplifier. So, the JFET current source sets the constant current I 15 through Zener diode D 2 making I 15 I z.Īs long as the Zener current (Iz) is between certain levels (Iz min and Iz max ) called holding current, the voltage across the Zener diode (V Z ) will be constantly working in the Voltage Regulation Area.Īs a result, the output current I 9 is almost constant even if the load resistance andor voltage changes. The gate will become negatively biased with regards to the source, negative values of V GS will start to shut Q 15 off.Įventually, a stable equilibrium will be attained through feedback, where V GS is just right for the current flowing through the JFET. With zero V GS the transistor enters in saturation region allowing a large current to flow through the JFET, so the current will increase.Īs the current increases, a voltage drop will develop across the Zener, until the diode will be reversed biased. Then the voltage drop across the Zener diode D2 and V GS will be zero. This stage highlighted in green color is formed by Q 1, Q 7, Q 13, Q 14, Q 15, R 1, R 9 and D 2. Jimmy Lin an RCA researcher ) following the classic 741 type opamp structure with some modifications.įind below the simplified circuit provided by JRC, broken down into blocks: Current Supply, Input Stage, Voltage Amplifier Stage (VAS), Output Stage (OPS) and Feedback Path.Ī stable current source is important in order to improve linearity and noise rejection. This IC was undoubtedly chosen in the beginning by Japanese design engineers because it was one of the cheapest dual opamps on the market with acceptable audio performance.Īs such, it was used in huge volumes of Japanese audio equipment.ĭespite its questionable audio performance, it seems to be well suited to duty in overdrive circuits. Many designers included this part in some of the most successful effects like the Orange Squeezer, DOD YJM 30, Boss OD1, Tube Screamer or Peavey equipment. The first RC4558 monolithic dual opamp was developed by Raytheon Semiconductors in 1974. This chip has industry standard pinout, meaning that there are several different suppliers manufacturing pin compatible 4558 devices and also it can replace other standard dual op-amps like the TL072, NE5532 or the OPA2134. The high voltage gain (100 dB typ.), good input impedance (5 M typ.) and versatile power supply ( 4 to 18 Volts) make it perfect to fit in pedal circuit designs. There most important reasons to use a current mirror are to enhance the gain and the signal integrity. Leave a Reply Cancel reply Your email address will not be published. Jumadi adalah seseorang yang menyukai dunia blogger dan menuliskan pengalaman service komputer, elektronik dan tips,trik internet. Jika menggunakan power suply simetris biasanya tegangan di pin Ground IC vertikal akan mendapat tegangan negatif. Datasheet LA78141 Datasheet sangat penting agar tidak merusak IC atau komponen lain di bagian Vertikal.
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