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co_buckfast

Member Since: April 30, 2012

Country: United States

  • News - According to Pete: Transi… | about 6 months ago

    Where’s the love for these transistor configurations? Don’t forget that opamps are merely multiple instantiations and variations of these transistor configurations (you’d need to add current mirrors, too).

    Common base? Useless? Look up cascode, a wicked great use of the common base.

    Emitter follower? Useless? What do you think is the transistor stage chosen for the output of many non rail-rail output stages? If you look at the size of a discrete transistor versus the size of a whole opamp, when you need more current output than the opamp can source, who you gonna call? Emitter follower, that’s who.

    The utility of these configurations is often seen by looking at the input and output impedances of the configuration:
    Low input impedances are typically driven with current sources, high input impedances are typically driven with voltage sources. Low output impedances make great voltage sources, high output impedances make great current sources. Then you can utilize feedback to accentuate good characteristics and suppress bad characteristics.

  • News - We Have It In Stock | about 8 months ago

    I’m in complete agreement. The setup for the story is complete nonsense.

    Good thing for SparkFun is if Nate ever gets lost or can’t fulfill his duties, a similar search for “Nate” on Digikey shows they have 79,780 Nate’s available. If even 10% of those are in stock, SparkFun can always get another Nate. (Well, if by Nate you mean some random RG178 coax cable that matches the search for Nate amongst all the other bogus Nate matches).

  • News - How to Build a Building | last year

    Excellent. I enjoy coming to pick up orders with my kids. Demos and exhibits will make them even more motivated to come along.

  • News - How to Build a Building | last year

    I hope the plan is to continue the option of “Local Pickup”?

  • News - Scratch Programming with … | last year

    Can the Simon board be used as an input to Scratch? Since children might often be introduced to electronics through the Simon game as a soldering project and it has the programming header, it would be neat to repurpose the board as an analog/digital input/output for Scratch. Anyone know how to do this?

  • Product BOB-09816 | about a year ago

    These opamps are in an inverting configuration. Look at IC1A in the schematic. There is an input branch (C5 + R2) and feedback branch (C1 // R1). Think of these 2 branches as a teeter totter with the opamp’s - input as the fulcrum. You can do the analysis to confirm this analogy works. In any case, when the input is above the - input, the output of the opamp will be below the - input and vice-versa. The problem arises that the power supplies for this breakout board are defined to be VCC and GND. There is no negative voltage. This is a common situation in a digital world; there is often only +V and GND. Thus, for this circuit to work properly, the - input has to be kept somewhat above GND to give the teeter totter some room to operate. That is why the voltage dividers are on the + inputs; this raises the - input (opamp will try to set its output to bring the - input to the same voltage as the + input) up to the reference + input. It turns out for general applications, ½ VCC is a pretty good place to put the fulcrum as the teeter totter can swing in both directions.

    The 1uF caps on the inputs AC couple (or remove the DC from) the inputs. This allows the teeter totter fulcrum to be reset nicely for each stage. Otherwise, any DC difference between the input signal and the reference being applied at the + input will be amplified.

  • Product PRT-00112 | about a year ago

    I don’t know if the supplier changed, but the plate is NOT Aluminum. A simple test with a magnet will verify…

  • Product COM-10878 | about a year ago

    It looks like all the El Escudo Dos digital pins are loaded with a series diode & 390 ohm resistor. I have an Arduino Uno. If I use the El Escudo Dos, am I losing the ability to use the external interrupts available on D2 and D3 (I’m trying to add an interrupt driven rotary encoder on the same project)?

    If so, is there a way on the El Escudo Dos, if I don’t need EL_A and EL_B, that I can recover the use of D2 and D3 without cutting traces, for instance. I’m thinking of cutting the shield pins for D2 and D3 as the most practical, reversible solution.

    A Leonardo is attractive, but I’d like to keep serial available for debugging.

  • News - New Product Friday: The p… | about a year ago

    Looks like you appreciate a “nice product” but not a nice nail polish job. No brush marks!

  • Product DEV-09718 | about 2 years ago

    The inductor on the schematic is most likely a ferrite bead and the 30 ohms is the impedance at a fairly high frequency like 100 MHz. The dc resistance is more likely 30-50 milliohms. Having said that, SparkFun should probably place a note on the schematic describing both the AC and DC resistances to better inform their customers.

No public wish lists :(